If you are developing a web-based service, Google Analytics is a free and really useful tool to analyse your traffic, your visitors and understand which content your customers are more interested in.
Google Analytics allows to visualise your number of vistor per day, week and month, their location and how they find you. In this way it will be easier for you to understand which communication channel works best for your customers and which area in the world is more valuable for your business.
Also, in Google Analytics you can set up an event goal to track specific behavious so that you can visualise how your visitors complete each step of a specific process you want to analyse (for example a check-out process)
To learn more simply watch this video and get started!