Acceptance testing is a process used in software development to determine if a system meets the required specifications and is ready for deployment. It involves evaluating the software from the end-user's perspective to ensure it functions as intended and fulfills business needs. This testing phase typically occurs after unit testing and integration testing. There are different types of acceptance testing, including user acceptance testing (UAT), where actual users test the software, and alpha and beta testing, which involve limited releases to gather feedback. Successful acceptance testing confirms that the software is reliable and ready for use in a real-world environment.