1. Load testing is testing an application under heavy loads, such as the testing of a web site under a range of loads to determine at what point the system response time will degrade or fail.

2. Load testing simulates the expected usage of a software program, by simulating multiple users that access the program's services concurrently. Load testing is most useful and most relevant for multi-user systems, client/server models, including web servers. For example, the load placed on the system is increased above normal usage patterns, in order to test the system's response at peak loads