Analytics are those little bits of code that allow you to track vital statistics of your blog. Things like:
1) How many people visited my blog
2) Where did they visit from
3) Which country are they from
4) How long did they read my blog
5) What’s my most viewed post?
All vital questions that allow you to better understand your visitors need and adjust the content accordingly.
The best analytics to use comes from google (like a lot of other things). So head on over to http://analytics.google.com and create an account, tie that to your blog and wait. Google Analytics will then give you a short code to paste in your blog, that code executes everytime someone visits your blog and google is informed of the visitors statistics. It then compiles all this information to display to you in graphical form.
Even if you know HTML and CSS, I’d suggest using one of the many google analytic plugins to install it, since it won’t run everytime you update your theme. For me I used Google Anlaytics for WordPress. It’s a very simple interface, and doesn’t require any code installation, all you need is a google account and google analytics setup and the plugin takes care of the rest.