Most significantly, unlike the geometries’ Count or equivalent inputs, the Amount input for the Duplicate node is a field input.
So, in previous versions doing the following would be non-trivial (whereas now it kinda is (if you’re familiar with GN)):
… before you had to come up with non-intuitive strategies to produce enough points and then distribute them in some way, or you had to over-produce points and then delete a random amount.
Also, just demonstrating points here… the Duplicate node works with other Domains also, e.g. Curves and Faces - which opens up a whole bunch of other generative features only available through convoluted “kludges” before.
Good luck.