Once you've set up with Google Analytics (see the blog post), there's a wealth of information to explore.
The 'traffic sources' overview tells you how people are getting to your website. Within this, you can see what search engines and direct links brought people there.
Within 'traffic sources', 'Google (organic)' means that people used "Google search" rather than clicking on a google ad - preferable as you don't pay for organic links. If this statistic rises over time, your search engine optimisation is working.
Also within 'traffic sources', 'Keywords' tells you what people actually typed in to search engines to reach you. This usually gives a mixed set of results, some surprising and others not so. Using this may help you to brainstorm other words and phrases to work into your content in order to attract more traffic.