**Load Testing:** Testing an application under heavy but expected load is known as Load Testing. Here, the load refers to the large volume of users, messages, requests, data, etc.
**Stress Testing**: When the load placed on the system is raised or accelerated beyond the normal range then it is known as Stress Testing.
**Volume Testing**: The process of checking the system, whether the system can handle the required amounts of data, user requests, etc. is known as Volume Testing.