Trackers are small features that are added to a webpage code, which compile different data and send it to some application or online service. This service analyzes that data and shows statistics of different aspects related to the users’ activity on the web. Some conclusions can be taken from those statistics analysis, which indicate, for example, whether there are more visits or less, if there is a most visited page, if the sales conversions are high or low, or if the bounce rate is normal or not, and more. These analytics can be useful to detect, correct or promote some aspects of a website. It is very recommendable, then, to implement some kind of tracking in your ecommerce that helps, for example, to optimize search engine positioning, to plan SEM campaigns or to measure the traffic that comes or the conversions.
The choice of a particular tracking type depends on the aspect of the ecommerce that you want to monitor and on the company or brand that supplies the service of tracking management.