Keyboard: CTRL + -; CTRL + SHIFT + -
Menu: View -> Navigate Backward; View -> Navigate Forward
Command: View.NavigateBackward; View.NavigateForward
The editor remembers locations when you move in a single command more than several lines away from where you are currently working, or if you edit in a particular location that is not adjacent to the last place you edited.
The goal is to remember interesting locations so that you can recall where you have been working without remembering so many locations the feature is not useful (such as every character typed, or every line entering several new lines of code one right after the other).
Doing a search, like Ctrl+F, drops a go-back marker at the found location.
So with all that, welcome back to the wonderful world of the Navigate buttons (and keyboard shortcuts, too)! These gems make travelling around your code much, much easier: