In the development of any application, it is not enough to simply build the program and release it right away. It needs to undergo a series of rigorous testing to ensure that the program passes the requirements of the client and has no bugs that can cause minor glitches or even serious problems later on. Alpha and beta testing are two of the stages that a software must undergo testing. Alpha testing occurs first and when the software passes that, beta testing can then be undertaken. If a software fails alpha testing, changes are done and it repeats the tests until the software passes.
Alpha testing is undergone by a small team of experts who knows how to find software faults. Although the team is only composed of a few members, their expertise allows them to catch majority of the problems by putting the software through all scenarios they can make and try any combination of inputs to coax the software into an error. With beta testing, the testers are no longer actual experts but the lack of expertise is made up by the sheer number. Depending on what the client wants, the beta version of the program can be released to a limited number of participants or to anybody who wants to. Participants in a beta test report errors and what they are doing or attempting to do at that very instant so that the developers can try to replicate the error and then find a fix for it.
During alpha testing, the program is still relatively rough and there may still be serious problems that can cause the program to crash. The limited number of alpha testers also mean that the program can only be tested on a limited number of hardware configurations. It may seem that the program is already working flawlessly during alpha testing but the different configurations of users can cause errors within the program. In beta testing, the task is more of polishing the program so that it works nicely for everyone rather than ensuring that it actually works. Problems are then patched prior to the release of the final version of the software.
Alpha testing occurs before beta testing
Alpha testing clears out most of the major bugs in a program while beta testing is more like polishing the program
Alpha testing is often not open to the public while beta testing can often involve the public