I have a question with exercise that I do not know where to start, it is an exercise of data path, and the statement asks to explain the functioning of the data path of the photo, I searched for videos on YouTube but delve into concepts that I do not understand Much, I started with this exercise because it seems to be simple, I do not know what concepts to start to explain the operation, if the names of the records involved, the movement of data, any help is appreciated 
This data path represents the first stage of the life cycle of an instruction, the IF (Instruction Fetching) stage, in which from the value of the PC (Program Counter) the instruction memory is accessed and the corresponding instruction is obtained.
The first element is the PC , a record that contains the memory address of the instruction to execute. After dumping the PC into the instruction memory, it is incremented by 4 (4 bytes, 32 bits) by the adder you see above. By increasing the PC we can repeat the cycle in the next instruction.
The value of the PC is passed to the instruction memory, which returns the value of the resident instruction in the memory location that is entered.