How to: View and Edit Code by Using Peek Definition (Alt+F12)
Visual Studio 2013
You can use the Peek Definition command to view and edit code without switching away from the code that you’re writing. Peek Definition and Go To Definition show the same information, but Peek Definition shows it in a pop-up window, and Go To Definition shows the code in a separate code window. Go To Definition causes your context (that is, the active code window, current line, and cursor position) to switch to the definition code window. By using Peek Definition, you can view and edit the definition and move around inside the definition file while keeping your place in the original code file.