No real difference in my mind, but that's because most SEO "experts" who specialize in and ONLY do SEO are a bunch of sleazy scam artists blowing smoke up your backside in the blind hope of emptying your wallet and then of course this here's a story 'bout Billy Joe and Bobby Sue
SEO is a small but important part of building a website -- but it has been turned into a cottage industry filled with lies and bunk populated by snake oil doctors and nube predators. They fabricate artificial statistical results to card-stack their nonsense into looking like it actually did something of value to your websites, to prey on the ignorance of those who only know it as a buzzword in passing.
SEO is NOT rocket science, and it goes with part of how I advocate building sites because there are only THREE things you really need to know and do:
1) Well written unique content of value. CONTENT FIRST!!!!!
2) Marked up semantically and properly cross-linked on the site (no, scripttardery like AJAX to replicate framesets for tabs, select for dropdowns as navigation instead of forms, and other "gee ain't it neat" bull is NOT "properly cross-linked"!)
3) With organically created (by visitors to your site) backlinks on relevant sites on similar topics.
Pretty much most EVERYTHING ELSE is 100% grade A farm fresh manure, and if it does have an impact that impact is basically the equivalent of dumping a can of shellac on a pile; no matter how much you polish it the end result is still just bug * on horse *.
Of cousre, most of what drives the SEO "industry" is more likely to get you slapped down the next time an engine makes a change to how it measures things as opposed to providing actual benefits -- see how the SEO-tards run around like chickens with their heads cut off every time Google makes an algorithm change. -- to the point many of them start crying if you even mention the words "penguin" or "hummingbird" -- meanwhile if you aren't using their pointless crap and stick to the basics, you'll get the same if not better traffic and such updates won't impact your ranking one way or the other!
See how the die hard SEO scammers repeatedly try to discredit Matt Cutts -- the head of Google's anti-spam division; aka the group that slaps them down for their abuse; when he said "write for the user, not the search engine" -- well, it may just be possible given his job he knows what he's talking about... so naturally the sleazy scumbags who have turned SEO into a sick buzzword to prey upon the ignorant try to discredit everything he says at every opportunity.
Hmm... SEO "experts" don't like what the guy who's in charge of determining what constitutes "abuse" of the system has to say... no, REALLY?
Naturally though, such abuse of buzzwords and fly-by-night scams will abound whenever you have people making information technology decisions who aren't qualified to do so; the proverbial "suits with checkbooks" who will "Give cash for vague promises" -- since the most they know about these topics is what they read in the financial trades. Or as I've said many a time "Getting technical advice from the pages of Forbes is like getting financial advice from the pages of Popular Electronics".
I mean, let's look at some of the SEO scam 'telltales'.
"Keyword Research" -- searching the web for keywords that people are searching for, that may not even be relevant to your TOPIC, then shoe-horning it into your content. If you have ANY clue what you are writing about or what your site is about, and RELEVANT words should already be there. This is just the old keyword stuffing nonsense in disguise, and if it DOES drive any traffic to your site, it's wasted bandwidth as since if the words AREN'T relevant, you just brought someone to your page who doesn't care about your topic.
"Magic search phrases" -- this is my name for them; it's a lie SEO scammers use to make their results look good. They cherry pick a phrase nobody actually uses on other sites or searches for, stuff it into their page, and then go "hey look, we're #1 for search for this phrase". Laughably, sometimes the words in the phrase aren't even used on those other sites in the same order.
"non competing competitors" -- this is an old marketing term used by the spin-doctor types to describe choosing companies you aren't actually in competition with, and using how well you are doing compared to them (as opposed to your real competition) to card stack things into looking better than they really are -- either to lie to investors for more operating capitol, or to artificially inflate your stock value before a buyout.
In terms of SEO, it's using things like "magic search phrases" to put yourself on a SERP (the actual listing PAGE, not the result, people screw that one up all the time) with sites that have nothing to do with the same topic.
About six or seven years ago I was on a (now defunct) forums where a total scam artist was leading the owner astray with his SEO-tard bull... and he used a "magic search phrase" for a Photoshop plug-in as 'proof' that he knew what he was talking about. He had come up with this BS phrase to say "Photoshop plug-in" that used neither word, and then bragged about how they were leading the search engines for that phrase.
Which means they ain't leading but two things when you realize the next 5,000 search results were about powder-coating automotive engines and auto-body repair.
ANY halfwit can make up some random phrase nobody else is using, and be listed #1 on the search engines for that exact phrase; yet the SEO-tard scam artists use exactly that to brag about how "good" they are. ... and frankly, if nobody else is using it or doing it, you might want to pause and think "Maybe there's a reason for that!"
"Paid backlinks" -- "Give us your money, we'll backlink to you from several dozen known scam sites and then leave you holding the bag." That's about as simple an explanation as I can come up with for this particular bit of idiocy. Sure, it'll work -- just long enough for them to get paid, then you get slapped down for participating in the scam and are back to square one.
"Paid Posters" -- I've seen this BURY more forums and blogs the past eight years or so than I can count. Happens a lot when sites or forums are 'flipped' to new owners, where the new owner doesn't actually know anything about owning a website and is desparate to drive more traffic for advertising revenue. Now defunct forums like DiscussAdmin and LovingTech come to mind....
The whole idea is you pay, and they have *teenage slave labor in Nigeria post random questions and other gibberish to your forums or blog so it looks like you have content; said random gibberish driving away every last legitimate user so you have no real traffic from real users -- killing activity by real members on the site inside a week, and killing the site itself inside six months.
* Slight exaggeration, it's more like underpaid sweatshops in South Korea and India... or worse, spam-bots that will get you slapped down for having "duplicate content" with other websites.
... and that's just the highlights of the card stacking, glittering generalities, transfer, bandwagon, and other propaganda-esque bull the average SEO "expert" will try to use to scam you -- When all you actually need to do is write "content of value" people might actually want, mark it up semantically, and promote it organically (social links on your page, get links in news articles / blogs by people who like your topic, etc).
Again, as Matt Cutts said, "Write for the user, not the search engine".
Anyone telling you much more than that is packing you so full of sand you could change your name to Sahara.