What is a poker tracker?

A poker tracker is a software that uses the poker hand history and compiles statistics and other analytical information from it, enabling players to self-analyze their gameplay after each game. It allows for instance session profit and loss monitoring, provides data such as hand count, time played, average winnings per hand/hour, cumulative balance etc. Most poker rooms allow the usage of such softwares as they do not interfere in the gameplay, but serve instead only as a statistical information source.