Chip 28nm and chip 7nm is the length of the transistor inside the chip is different. The transistor length of the 28nm chip is 28nm, and the transistor length of the 7nm chip is 7nm. The 28nm chip is two generations behind the 7nm chip, and the power reaction speed is not as fast as the 7nm chip. The 28nm chip is satisfied by most devices, and the 7nm chip is mainly used in devices with higher chip sizes such as mobile phones.
The chip 28nm is an early processor 7nm is a recently released processor compared to the former in terms of processing speed, performance and power consumption optimization.