A tag is a keyword or label that categorizes your question with other, similar questions. Using the right tags makes it easier for others to find and answer your question.
an Emacs presentation feature that alters the appearance of a buffer’s text on the screen, without changing the buffer content
GNU Project Debugger - Start it via `M-x gdb` to run the debugger on Ada, C, C++, Objective-C, Pascal, Fortran, Java and other languages.
The generic concept of automatically saving information to the disk or to a remote server, triggered by a timer or any other event inside of Emacs.