The basics of gcode. First of all, it’s just text with basically one command per line. The units are usually mm, but some gcode interpreters allow other units via a gcode command that sets it.

G1 X6.476 Y17.116 E0.05057 F1800.000 T1

The first bit G1 is the gcode command. G1 is “controlled move”. The rest of the line are parameters to that command. In this case, positions specified in millimeters. The positions may be relative to the current position or absolute which depends on the mode. Other gcode commands select (G90 and G91) absolute or relative. Positive X is generally to the right and positive Y is away from the front of the machine.

Different devices choose the origin of the absolute coordinates to be in different places. The typical 0,0 for many open source printers is the front left corner when facing the printer. The typical for delta style printers and MakerBot printers or there clones is the center of the bed.

So the coordinates X & Y is the position on the coordinate plane (there’s also Z). What’s the rest of it?

E is the extruder position. There might be more than one, so the E coordinate is for the currently selected extruder. It is also absolute if the others are so to extrude 5mm _more_plastic it has to be 5 more than the last command.

F is the feedrate. The units are in mm per minute. That’s just how fast should the bot travel to get to the specified location.

T is the tool selector parameter. The tool numbers count from zero. For my bot, T0 is the right hand extruder and T1 is the left.