What is the difference between Extract and Separate in Maya's modeling set.

extract extracts faces from a mesh, separate separates pieces based on the border edges

so, if you have a cube, you select a face and go extract the you've taken that face off from the cube and now you have two distinct pieces of geometry

if you did separate on that same face nothing will happen

essentially separate is the exact opposite of combine and extract the opposite of append polygon

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that's a "Ch" pronounced as a "K"

Computer skills I should have:
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as Chirone said extract extracts the selected face(s) from the geometry and separate separates the combined geometries........