Application testing refers to the testing of the overall software application behavior or both front end and back end functionalities along with load testing. It involves a set of activities through manual or automation or both scripts which aim to unveil errors in the software application.
It covers the entire end to end functional testing of a software application. Such type of testing helps the team to evaluate and enhance the software quality and at the same time, it reduces the software development and testing costs to the organization.
Application testing can be thought as a bundle of tests which covers front-end testing or GUI testing, back-end testing or database testing, load testing, etc.