A feature release is when new features or enhancements are made available. A feature release constitutes a major version and is noted by an increment in the version number on either side of the first decimal.
Product Name x.y
A maintenance release is when maintenance requirements are instituted for a feature release. A maintenance updates is a minor release and is noted by an increment in the version number to the right of the 2nd decimal.
Product Name 2.7.x
A patch release is when fixes are instituted for any release between major or minor release cycles. Patches are generally made to address high severity bugs or security issues.
Product Name 2.7.1.x