Windows 10 is a series of operating systems developed by Microsoft. It is the successor to Windows 8.1.
New feature updates for Windows 10 are released twice a year, around March and September. These versions receive monthly quality updates for 18 or 30 months from the date of the release, depending upon the release lifecycle.
For more information about Windows 10 update lifecycle, and a list of currently supported versions, see Windows Lifecycle Fact Sheet.