Following definitions are according to ISTQB syllabus (International Software Testing Qualification Board, something like a standardisation gremium) "Load testing" tests the behaviour of a system (or component or whatever) with increased load, e.g. the number of users on the system, number of transactions etc... Goal is to determine what load can be handled by the system. "Stress testing" evaluates a system at or beyond the limit of its specified requirements. Since that is exactly what you need to do for load testing (to see how much your system can handle), both, load and stress testing can be regarded equivalent. "Performance testing" determines the performance of a system, i.e. the degree to which the system accomplishes its tasks within given constraints in terms of time and throughput rate. Example: You have designed your system for 10 users. In load / stress testing, you test its behaviour with 1 user, 2 users, ... 10 users, 11 users. Focus of your test here is not the speed (it may get terribly slow with 10 users) of the system but if it does not break, if it really allows 10 users (and not only 8) etc. In performance test, you verify that your system meets given timing constraints. For example, if your requirement is that the system should respond within 10 seconds in any case, you will focus on stopping the time. Of course, you will have to test the speed with a different number of users (1,2 ... 10) logged in, since that may affect the system. So somehow, both test strategies are intertwined. Did this help a little bit???