Theme from Scratch

I know XHTML and a bit of CSS, but I am just starting to delve in PHP. Looking at the default template, it’s a little daunting to see a bunch of PHP where I have no clue what it does (and despite all the information in wordpress CODEX, it’s not like it’s a step by step tutorial – I find it very confusing to follow).

This is a really simple question because this is what I can tell with my limited knowledge.

Basically all WordPress files are is HTML contents wrapped up in PHP telling the web page where to get and put information.

So I can just build the front page for example completely in XHTML and CSS, then just wrap PHP code around it?

I haven’t found any tutorials online that really elaborate on this and I don’t have the funds to hire a web designer.