In software development, a beta test is the second phase
of software testing in which a sampling of the intended
audience tries the product out. (Beta is the second letter of
the Greek alphabet.) Originally, the term alpha test meant
the first phase of testing in a software development
process. The first phase includes unit testing, component
testing, and system testing. Beta testing can be considered
"pre-release testing." Beta test versions of software are now
distributed to a wide audience on the Web partly to give the
program a "real-world" test and partly to provide a preview
of the next release.
http://whatis.techtarget.com/definition/beta-test