Taco is a measure of how many times the engine turns, bit like an odometer on a car is a measure of how many times the wheels turn round. This is usualy a mechanical device.
A hobbs meter usualy starts running when typically either the electrics are turned on or oil pressure is registered. Note, this is irrespective of what the engine is doing. This is usualy an electrical device.
I heard of a hobbs meter on a twin wired up to start when the under carrige was raised. Also heard that a lot of people flew with the wheels down, not unsurprisingly.
HTH
PS