Alpha Test: The first test of newly developed, when the first round of bugs has been fixed the product goes with actual users for testing. For custom software the customer may be invited into the vendor's facilities for an alpha test to ensure the client's vision has been interpreted properly by the developer.
Beta Test: A test of new or revised software application that is performed by users at their facilities under normal operating conditions. Beta testing follows alpha testing. Vendors of packaged software often offer their customers the opportunity of beta testing new releases or versions and the beta testing of elaborate products such as operating systems can take months.
Acceptance testing: Testing is performed by the Client of the application to determine whether the application is developed as per the requirements specified by him/her. It is performed within the development of the organization or at the client site.