what is performance testing?

Performance is not just a single word but is a cohesion of many other quality attributes like scalability, reliability and stability of the software. Though the software is functionally absolute (at least with not many errors) it is branded as failure when less reliable, as reliability is the key consideration in the world of business. An unnoticed error in the software would lead to the financial catastrophe.

So the answer to what is performance testing? Could be estimates of various performance characteristics that end users are likely to encounter when using the application. Performance testing is (most frequently) conducted to determine whether or not an application will do what it is intended to do acceptably in reality. Identification of existing or potential functional errors that aren't detectable with single-user scenarios but can or will manifest under multi-user scenarios. There is no protocol that a website should maintain particular minimum response time. Hence performance testing becomes more complex. If a site takes 8 min and another takes 3 min definitely the users flock to the product which would respond in less time or perform better.

Performance testing is the most important aspect in the world of software testing as the performance defects would lead to an utter failure of the product however functionally perfect (fewer errors).