Hi Brian, for an actual duplicate you would use something else, like Transform / Copy, Array, Ctrl+Drag, or copy/paste.

Offset creates a new curve or surface that is a given distance away from an existing one. It kind of traces an outline that is a distance away, it is not the same thing as a duplicate.

Here is another example - given this starting curve:



Doing an offset of distance 3, clicking to the top side (you can pick which side to offset to), will generate this:




The second curve is not an exact duplicate of the first, it is basically a parallel result, with extensions for corners.

You use it for things where you want parallel curves or surfaces that form a particular thickness between the 2 parallel pieces. You can't normally make a parallel curve by just an exact duplication except for the case of a simple line segment.

Let me know if that doesn't answer your question, that is more about the actual output of Offset, the workflow for using it has a couple of different modes you can set, like through point mode or given distance mode.

- Michael