They are results of the hosting process feature that was introduced for the first time with VS2005.

Hosting process file, with extension .vshosts.exe, serves main three purposes:

• Improving debugging performance
• Enabling partial trust debugging
• Enabling design time expression evaluation

There are more files created with the vshost file for the Visual Studio project:

• .pdb or the Programm DataBase that contains debug symbols
• .vshost.exe.manifest that contains mostly dependencies on libraries

Also, notice that these files shouldn’t be deployed with the application you finished or run directly.

It’s possible to disable generation vshost files under project settings -> Debug options -> Enable the Visual Studio hosting process checkbox.

You can find more information about the advanced debugging features in a MSDN article.