If you wish to offer services from you server(s). For example, host a website. You should have a dedicated IP address so that people around the world can connect to your service. Think of an IP address as a telephone number. If your running a business it would be a smart idea to have the same phone number all the time rather than having a different phone number every day - wouldn't it? Otherwise you probably wouldn't get any phone calls!
They are not offering 16 dedicated IPs for the one domain, they are offering it for the one account. If you host 10,000 domains on the one account then you may need more than the 16 dedicated IPs that are offered.
Generally you need a dedicated IP if you need pages that have a domain specific security certificate or need to open specific ports on the domain. Other domains can share an account and IP address without any problems.
As the previous speakers outlined, you don't necessarily need an own IP address, but it makes things easier:
1. You need an own IP if you wish to get a SSL certificate for your website that matches your domain name.
2. For e-commerce websites I consider it as a sign of trust to have an own IP address and not share one with hundreds of other domains. Especially when the admin address of the IP is set to the business owner (but likely your webhoster doesn't allow this unless you get a high-priced dedicated server).
3. Some applications profit from an own IP address. For example, if you intend to send out newsletters to your customers, depending upon their spam filters, your mails have higher chances to go through when the mail server matches your domain and your IP.
4. Generally an own IP also plays a role for search engine marketing and position ranking.
some hosts provide Dedicated IP, what is it used for?
could you explain?
Dedicated IP means Unique IP address for your own website. It does not share with another account. I have got a Dedicated IP address for my website from this site www.XnYnZ.com .
Eventhough your domain name is not available like getting late go to your website at that time just enter your Dedicated IP address into the web browser bar it will automatically go to your website. This is the main benefit for get a Dedicated IP.