Is PC4 same as DDR4?

The number after DDR/PC and before the hyphen refers to the generation: DDR2 is PC2, DDR3 is PC3, DDR4 is PC4.

What does PC4 3200 mean in RAM?

I believe “DDR4” refers to the memory chips themselves while “PC4” refers to the DIMM, the memory stick you plug into the slot. For example, DDR4-3200 refers to a memory chip that runs at 3200MT/s (megatransfers per second) while PC4-25600 refers to a DIMM that transfers 25.6GB/s.