All I understand, are the codes for HTML and CSS are quite different.
I haven’t checked out XHTML yet, though what is the difference?
Which is best to use … and why?
To keep it simple, HTML is the basis of every website. CSS is a stylesheet which you can use to have the same fonts and colours for example on every web page.
HTML and XHTML are essentially the same thing, XHTML is stricter in how its interpreted. They are both used to structure a web page whereas CSS (Cascading Style Sheet) is used to provide styling information.
If you are just starting out then stick with HTML and CSS.
XHTML is not for PDAs and televisions. Its simply on a slightly different branch of markup tree. xhtml has its roots in XML whereas HTML has its roots in SGML.
Don’t worry about the difference until you are more familiar with HTML. Stick with that for a while and then have a look at XHTML. html is still by far the markup language used for the web.