I'm wondering the difference between the 'least count' and the 'smallest division' of an instrument. Can you explain that for me, plz?
Welcome to physics.se.
It is the difference between continuous and discreet.
A least count, for example in a geiger counter, would be an integer number=1 since one can detect single hits.
A smallest division will be given by a real number. In voltmeters for example the division is continuous because the potential is a continuous quantity.
Both should be accompanied by a +/- error.