Difference Between Build and Re-Build in Visual Studio .Net?

Build means compile and link only the source files that have changed since the last build, while Rebuild means compile and link all source files regardless of whether they changed or not. Build is the normal thing to do and is faster. Sometimes the versions of project target components can get out of sync and rebuild is necessary to make the build successful. In practice, you never need to Clean.

Build or Rebuild Solution builds or rebuilds all projects in the your solution, while Build or Rebuild <project name> builds or rebuilds the StartUp project. To set the StartUp project, right click on the desired project name in the Solution Explorer tab and select Set as StartUp project. The project name now appears in bold.

Build.BuildSolution F6 or CTRL+SHIFT+B Builds all the projects in the solution.
Build.BuildSelection SHIFT+F6 Builds the selected project
and its dependencies.

Hope this helps