Normally I would answer this question with a simple link to a Google search but in this case I'll make an exception and add some more information too :P
Basically there are several methods for tracking web traffic to your website.
Most hosting providers also offer you a basic statistics package available at www.yourdomain.com/stats (or something similar)
Alternately, you can write your own tracking software but this is often more work than it's worth with the number of free tracking services already available online.
Hope this helps :) Please remember to mark the thread solved once your issue is resolved.
You can add Google analytics to your site. It's free.
And you can also get that service from your hosting provider. But you will have to pay for it.