Load testing is a performance test to measure and evaluate the performance behaviors and ability of your system to continue to function properly under different workloads. The goal of load testing is to determine and ensure that the system functions properly beyond the expected maximum workload. Additionally, load testing evaluates the performance characteristics such as response times, transaction rates, and other time sensitive issues.
Volume testing identifies the continuous maximum load or volume that your system can handle for a given period. For example, if the system is processing a set of database records to generate a report, a Volume Test would use a large test database and check that the software behaved normally and produced the correct report.
The goal of Performance testing is to verify performance requirements have been achieved.