Help needed, Craftsman wood planer.

[Daturat100r]

A jointer is used for flattening boards, a planner is used to get them to the desired thickness. The sequence from rough milled lumber is-
Jointers are used to establish a flat face, then a square edge on a board. then it can be run through the thicknessing planer to flatten the other face parallel to the other. Then the board can be run through tight against the fence to establish an edge square to the faces.

Most jointers also have the ability to create a rabbet on the edge of the board. They also are useful, if sharp & well adjusted, to prepare edges for gluing up large panels.

Look at the words used to describe these machines,Plane is a geometric term for a flat surface.
"Planer" is a machine that forms a plane on the work passed over it as with a "Jointer",the term thicknesser makes one surface parrallel to the other and does not itself correct non-planer work.
The term planer/thicknesser most likely came from under and over machines or two siders which both have the ability to make a board face a plane the first in two operations on same machine the second machine does it all in one pass be it a 2 or 4 sider.
Confusion over terminology ,especially as the woodworking trade amongst other love to have their own terminlogy, is most likely due to regional usage that evolves and changes with time.