About homing and switches...

[JAZZCNC]

Paulus.v Explanation of Homing on an index is spot on, however, I think you'll find that most Closed-loop Hybrid servo encoders don't provide an index Pulse so can't use that feature.

Regards Homing and Zeroing etc then you need to get into the habit of thinking in terms of Machine coordinates and Work coordinates. Home switches define the Absolute ZERO machine coordinate position. This positon NEVER changes and is used to reference WORK coordinate ZERO.
So when you send the machine to HOME your sending it Machine ZERO. From this position, you can also define machine limits.

WORK zero can be anywhere inside the work envelope of the machine. You'll often see reference to WORK offsets, these are just areas inside of the machine work area which can have separate WORK zero positions.
This means you can assign each area to a Fixture G-code ie: G54 G55 G56 etc and use these codes in your cutting G-code file so it moves to the next fixture and starts cutting from new Zero point.
This is useful for instance when have several different parts or materials setups on the bed. For instance could have G54 reference to point on the Bed while G55 references to corner of a Vice and so on.
Each would have there own Zero WORK coordinate and all are referenced from the MACHINE Zero.(HOME). From MACHINE ZERO any location inside any Fixture Offset can be located accurately.