It's a "fragment" or "named anchor". You can you use to link to part of a document. Typically when you link to a page, the browser opens it up at the top of the page. But you link to a section half-way down, you can use the fragment to link to that heading (or whatever).
If there is no <a name="whatever"/> tag within the page, then the browser will just link to the top of the page. If the fragment is empty, then it will also just link to the top of the page.
For a fragment only <a href="#">Link name</a>, then that's just a link to the top of the current page.
You often see that kind of link used in conjuction with javascript. Standards compliant HTML requires a href attribute, but if you're planning to handle the request with javascript then "#" serves as a reasonable place holder.
与恶龙缠斗过久,自身亦成为恶龙；凝视深渊过久,深渊将回以凝视…
