Difference overview between Control Flow and Data Flow tasks

Two most important sections in a SSIS package are Control flow tasks and Data flow tasks. But beginners commonly get confused while deciding where control flow task and where data flow task should be used.

Here I am explaining the difference between these two categories of tasks with example of goods transport system.

What are common steps in a transport system? Forgive me I am not an expert of transport system so may be that I am not in correct in this scenario. Let us discuss common steps.

1.       Taking order from client

2.       Generating invoice

3.       Receiving payment

4.       Transferring the material from source location to destination

5.       Confirming to client for successful transfer of material

This whole process can be divided into two parts:
A. Preparing and controlling the transportation. (step 1,2,3,5)
B. Transferring the material (step 4)
In the same way the process of data transfer in SSIS is also divided into two parts. All tasks of part A are implemented using Control Flow tasks while actual data transfer (part B) is implemented using Data Flow tasks.