If you have a website, Google analytics is the most reliable tool to check the traffic coming to your website. You can check the major traffic sources, keywords, most performing pages etc in Google analytics.

It can track visitors from all referrers, including search engines and social networks, direct visits and referring sites.

Google Analytics are used to check no. of visitors coming to a site. It give detailed information about visitors i.e From which source or which country visitors are coming from.

Google Analytics is implemented with "page tags". A page tag, in this case called the Google Analytics Tracking Code (GATC) is a snippet of JavaScript code that the website owner user adds to every page of the website. The GATC code runs in the client browser when the client browses the page (if JavaScript is enabled in the browser) and collects visitor data and sends it to a Google data collection server as part of a request for a web beacon.

Google Analytics is a service offered by Google that generates detailed statistics about a website's traffic and traffic sources and measures conversions and sales. The product is aimed at marketers as opposed to webmasters and technologists from which the industry of web analytic originally grew. It is the most widely used website statistics service.