There are three main types of "ground" in the circuit, power ground, signal ground, earth, Vcc or Vdd is connected to +5v, Gnd ground, digital and analog ground and the final point of the ground **** ground, and ultimately whether it is really connected to the earth, the circuit diagram is generally not expressed. And a vertical and horizontal grounding indicates that the chassis, not connected to earth.
GND is the abbreviation of the ground end of the wire. It stands for ground or 0 wire. This ground is not really a ground, it is a ground assumed for application purposes, and for power supplies it is the negative terminal of a power supply.
Power ground is mainly for the path taken by the power circuit current, generally speaking the power ground flows a larger current, while the signal ground is mainly for the path taken by the return of communication signals between two chips or modules, generally speaking the signal ground flows a very small current, in fact, both of them are GND.
Extended information:
The purpose of signal circuit grounding:
To ensure that the signal has a stable reference potential. In order to make the electronic equipment work with a uniform reference potential, to avoid the interference of harmful electromagnetic fields, so that the electronic equipment stable and reliable work, the signal circuit in the electronic equipment should be grounded, referred to as the signal ground.
Reference:
Baidu Encyclopedia-GNDReference:
Baidu Encyclopedia-GND