A symbolic debugger such as GDB can run your program, just like you can. However, with the magic of including debugging symbols in the executable, the debugger gives the illusion of executing the program line by line of source code, instead of instruction by instruction of compiled machine code. This seemingly humble fact is precisely what makes a symbolic debugger so useful in debugging programs.
If all the debugger could do is run a program, it wouldn't be of much use to us. We could certainly do the same thing, and more efficiently, to boot. The usefulness of the debugger lies in the fact that we can instruct it to pause execution of the program. Once paused, the debugger gives us a chance to inspect variables, trace the execution path, and much more.
There are three ways to instruct GDB to pause execution of your program:
Confusingly (at first), all three mechanisms are collectively termed breakpoints in the GDB documentation. This may be because they share many of the same attributes and commands. For example, you'll learn about GDB's delete command which, as the help blurb says, deletes a breakpoint:
(gdb) help delete Delete some breakpoints or auto-display expressions. Arguments are breakpoint numbers with spaces in between. To delete all breakpoints, give no argument.
However, the experienced GDB user knows that the help blurb really means the delete command deletes breakpoints, watchpoints, and catchpoints!