one
The numbers are different,4nm refers to 4 nanometers,5nm refers to 5 nanometers.
two
In the case of electronics, it means the process. The 4nm process is shorter and more transistors can be accommodated on a chip in the same area. The better the performance of the chip.
three
Due to the failure of Moore's Law now, and the different names of various manufacturers, the actual experience is no different between 4nm and 5nm.