ASP, PHP, Perl, JSP, Coldfussion and Ruby are all server side languages that are used to build dynamic websites like this one.
Comparing ASP and PHP is sorta (not completely) like comparing Windows and Linux. If you are going the Windows - IIS route or are familiar with Visual Basic or are making an ecommerce site then ASP would be a good choice. Otherwise PHP or Ruby would be a better choice.
Coldfusion is the version made by Macromedia and JSP is Java's server side programing language.
If you are just starting out and trying to decide on the path you want to take then I would recommend
Ruby or
PHP. I wouldn't use the word rubbish to describe the others but I would recommend skipping them.
If you want to be a web developer then I recommend going in this order.
1. A very good understanding of XHTML.
2. A very good understanding of CSS.
3. Basic understanding of Ruby or PHP.
4. Basic understanding of mySQL.
5. Basic understanding of Linux.
6. Basic understanding of Apache or similar.
7. Go back and master each one in the same order.