What is a load and performance test
A load test checks and measures the performance of a system under several workloads. This may be crucial, for example, prior to a release deployment or going-live as well as during the software development process and run (operations) of an application.
If you expect an uncommonly higher load (e.g. before an Black Friday event, university enrollment, etc.) or intensive use of the services or a website you perform at least a basic load and performance test scenario to ensure the stability, load-robustness and stable run of your application.
To figure out where weaknesses and limits are hidden in a system, it is subjected to a continously increasing load until it can no longer withstand the stress (load test type: stress test/ overload scenario). This works by simulating high payload, either in form of many concurrent users (concurrent VUs) or fast repeating actions (high throughput through small think time). This allows you to spot any errors that occur only under high or higher system load. The load test focuses on measuring the time and consumption behaviour.
The load test or performance test deals with this. It measures how the response and processing speed behaves at different loads on the system.
In the SLC/ ALC (software/ application life cycle) load and performance tests are usually found in the software development phase in the area of quality assurance activities (software test), in integration or system test. As a rule, a load test always involves a kind of test automation, since normally one would not want to apply the load with tens of thousands of manual testers, but rather leaves this to virtual users (VUs) in form of test scripts which run on load generators via dedicated load test software.
Performance tests are generally sorted into non-functional tests inbetween software testing.
You may have encountered load tests under abbreviations like LuP or LPT (both: Load & Performance Test).