The commands in the G-code files are read by the machine controller which then sends signals to various components of the machine to execute such as motor controllers and coolant pump. 

The G-code file must be produced from the same CAD software that is used to design the component.

G-code file format and commands share many similarities across different machines, from 3D printers, to laser/plasma cutters, water jet cutters and CNC milling and lathe machines. 

A G-code file is a text file with a command on each line.

Each G-code file is produced specifically for a certain machine and contains machine specific commands and also takes into consideration the available workspace and machine capabilities.

A G-code file can only be produced by CAM software. It cannot be written or edited directly using a text editor.

A G-code is a binary file and could also be encrypted.