Units are usually made up of a number of models of the same type. It therefore follows that a unit of, say, ten models each of, let us assume, 9 points is worth a total of 10 x 9 = 90 points. It is quite usual to refer to a unit in terms of its value, so you might hear players talk of 'a 140 point unit of Orc warriors', '150 points of High Elf archers', or some such expression. As most practically sized units are likely to be between 100 and 300 points, it can be assumed that a 2,000 point army would have about ten units.

However, this doesn't allow for character models. Once points have been allocated for these important pieces the typical 2,000 point army is more likely to have about seven units in total, of which some might be a single piece such as a chariot or war machine.

Obviously this varies; we need only consider the matter here insofar as it gives a fair idea of what's meant by a 2,000 point army.