Alpha testing is the preliminary phase of testing of the development of software. When the development is about to complete, alpha testing is done in a lab environment within the in house teams. Basically the simulation is done. Fixing of bugs and minor changes in design may also be carried out if necessary. With this type of testing reliability is ascertained and the early detection of error helps a lot at this stage.
Beta testing is the secondary phase of testing which is done in real environment and with the end users. So the real end users take the opportunity to test it and provide their input in respect of design, functionality and usuability of the product. It reduces the failure risk and the success at this stage paves the way for the final release of the product. The customer feedback at this stage plays a greater role in improving the product quality.