Alexa allows you to basically analyse the website traffic, it helps you to get the information about the website such as the alexa rankings this means that is lower the rank the more the traffic to the website is.
It also shows the most popular country for that website traffic, It also shows a lot of cool information such as bounce rate of the website, if you are anywhere remotely connected to online business or internet marketing this is the must have tool for you.
It also has a very cool chrome browser plugin which you may choose to install and its very useful. Overall checkout this tool and benefit from it.