Control flow refers to the means for controlling the order in which sections of a program are executed.
The underlying CPU's instruction set will have a number of transfer of control primitives: jump/branch, both un-conditional as well as conditional branches; and subroutine calls.
Programming languages often add additional mechanisms, particularly block structures, in which a group of instructions are treated as a unit for various control flow mechanisms (e.g. loops, conditional if-then-else constructs, etc).
Blocks are also often used to control the scope over which variables (particularly local variables) are accessible.
Interrupts and exceptions also divert the flow of control in a computer, but at times which are not always predictable.