Set absolute distance mode.
In absolute position mode machine will move to the commanded position in the active user coordinate system.
G90 is a G-code used to set the distance mode to absolute. It means that all coordinates are given in reference to the machine's zero point or reference position. With the G90 mode, the machine will move to the exact coordinates specified in the G-code program.
For example, if a G-code program has the command G90 G0 X10 Y5 Z0, the machine will move to the exact coordinates (10,5,0) regardless of its current position.
G90 is used in contrast with G91, which is used to set the distance mode to incremental. In incremental mode, the machine will move to a position relative to its current position, rather than to a specific absolute coordinate.
G90
G90