Traditional procedural programming languages typically require programmers to define an explicit "flow of control" at every stage in their programs. Mathematica provides standard flow control primitives, with various symbolic extensions—though its higher-level programming paradigm usually frees programmers from having to specify the details of flow control.
Return — return from any function
Check — check for messages
Abort — generate an abort
Pause — pause for a specified time
Dialog — initiate a subsession dialog