The term 'prerelease version' refers to a version of a product that is released before the official launch. The most common type of prerelease version is the BETA version, which is usually released to a limited number of users for testing and feedback. BETA versions are typically marked with the letter 'B' followed by a number, such as B1 or B2. This allows developers to track the progress of the product and make changes based on user feedback.