The term ‘unit’ refers to military formations
that are represented by a single ‘counter’ and
can be moved independently on the game map.
No, in RUS, these are 'stack' or 'force', or 'group of units'.
A stack is not a unit, but a force can be (composed of) a single unit.
Units are individual figures (Commandants, mainly Brigades, Divisions, Corps and Army) we can see in forces.
(That's I succeded in learning in the tutorials)
Units can vary in size from full Division,
Brigades, Regiments, artillery batteries, Army
HQs, and even individual Leaders.
No for regiments and artillery batteries: Elements are not units.
A unit is to a force what an element is to a unit
(but a unit can be composed of other units, as for Divisions).
These bad definitions are mainly why the tutorials are confusing. I think this problem is from the scale of the game.