Terminology:

A block diagram is a pictorial representation of the cause and effect relationship among the input and output of a physical system. A block diagram gives a means to simply identify the functional relationships between the several parts of a control system.

The simplest form of a block diagram is the block and arrows diagram. That consists of a single block along with one input and one outcome. The block generally holds the name of the element or the symbol of a mathematical operation to be performed on the input to acquire the desired outcome. Arrows identify the direction of information or signal flow.