What is semantic markup, and why would I want to use that?

Question

Like it says.

Answer 1

From http://www.digital-web.com/articles/writing_semantic_markup/ :

semantic markup is markup that is descriptive enough to allow us and the machines we program to recognize it and make decisions about it. In other words, markup means something when we can identify it and do useful things with it. In this way, semantic markup becomes more than merely descriptive. It becomes a brilliant mechanism that allows both humans and machines to “understand” the same information.