That'll link to page2.htm and then tell the browser to scroll down to the element (such as a header) that has the id of section3. e.g.
<p>Check out <a href="page2.htm#section3">section 3 of page 2</a>! Aint that just hoopy?</p>
<h2 id="section3">Section 3: Best of one and two</h2>
Disclaimer. (1) Whilst I will help you sometimes, if I feel like it, and my advice in relation to your actual question will be of good quality: my posts are to be taken with a pinch of salt. I will be sarcastic, deploy irony and include obscure cultural references for my own amusement without warning.
(2) You will gain nothing from complaining, and if you try to argue with me then you will not win. No matter how noble your battle seems, I am still better than you, don't be an hero.