Alpha testing relates to the first round of testing. Beta testing refers to the second round of testing.
Before releasing new software on to the market, developers will test it in-house. This is alpha testing.
The developers will then trial the software with a limited number of users. The users report any problems to the developers. This is called beta testing. Once the developers are confident that the software works, they will release it for sale or distribution.
The final test is when the product is released and real end users begin using it. Very often, end users find things wrong with systems that the programmers did not expect.
Updates are often released for operating systems, applications and games because customers have found software bugs. Reporting errors online to the developers allows them to investigate what has gone wrong. The developers can then fix the problems and release updates.