Load and performance testing is a non functional testing.
Performance testing allow tester to judge how well an application or website performs under specific circumstance .
Measuring the time taken, the scalability and reliability of an action is key to performance testing.
Performance test and Load/Stress Test determine the ability of the application to perform while under load.
During Stress / Load testing the tester attempts to stress or load an aspect of the system to the point of failure.
- the goal being to determine weak points in the system architecture.
reference: http://www.automationanywhere.com/Testing/solutions/automated-performance