The Lathe Modifier

Starting off with a rectangle I used the line tool to create a long shape inside the rectangle, after creating the shape I deleted the rectangle as it was only for a guide.

I added the lathe modifier to the shape and it created a strange object.

This was because all it had done was rotate the shape on its axis.

Selecting the Min option changes the point at which the object is rotated to the minimum point on the x axis.

This gave a shape like this: