what can an ad network track with ?

hi,

coding noob here.

i would like to understand the following:

what can an ad network (cpm) track when i insert their javascript code in my wordpress blog.
what kind of data can they collect from my site?

the code looks like this:

<script type='text/javascript' src='//someblabla/apu.php?zoneid=1234567'></script>

thank you

Since it's Javascript, anything browser-side really. Research ECMA and what most browsers allow access to. It's more than you think!

Screen size,
IP,
Operating System,
Browser,
Time-on-site,
Anything Google Analytics tracks ;-)