Version vs service pack in windows what is difference between them

When MS releases a new Operating System, it assigns it a Build Number. Over time, after the release MS updates the system to improve security or enhance the system performance. After some period of time, historically about a year after first release, MS will assemble the updates from the system's release into a Service Pack containing the cumulative updates. The Service packs allow someone doing a re-install of the operating system to use the Service Pack to install, or to slipstream, all the critical updates using the Service Pack instead of spending hours downloading them from microsoft update.