Whats the difference between a limit switch & a Homing switch?

Is there a video or instructions that shows how to install & calibrate both of them them?

Thanks

No calibration required, they just work
The difference is simply one is used to tell the control you have reached the limits and to E-Stop, the other is to tell the control where the machine coords zeros should be set so that the control  knows where it is.

With Mach you can share Limit and Home switches on each axis or you can have them separate, it all depends on your setup whether one way is better than the other.
For example you may just be using the parallel port and have a relatively small travel, in that case there are no real benefits to have separate switches. If however you have a controller that can home to an Index pulse then it is better to have separate home switches. Also a machine with large travels may benefit from separate home switches as you would not have to travel so far when homiing.
Hood