In general, versioning is a product development practice where a single product is created with various, distinct versions, either from inception or over the course of time. In versioning, each new version of a product represents an upgrade with improved functionality and/or feature sets.
Software versioning is versioning for computer software, and has it’s own special set of conventions. In software versioning, new versions of software are numbered to indicate the type of changes made. These numbers appear following the name of the software, in sets of three, and are separated by periods. The first number changes if there are upgrades to the major functionality of the software. The second number changes if new features are added. The third number changes if bugs have been purged since the last version.
http://searchsoftwarequality.techtarget.com/definition/versioning http://en.wikipedia.org/wiki/Software_versioning http://www.investopedia.com/terms/v/versioning.asp