There is a lot of information on this topic on google. You might try
looking there as well.

A jointer makes wood flat and makes two edges meet at a specified angle
(usually 90 degrees).

A planer (without additional jigs) makes your wood uniform thickness,
but not necessarily flat.


There are ways to work around not having a jointer:

You can use a sled to make wood flat in a planer, there are various
plans available for this.

You can use a jig with a tablesaw/router get your edges straight.



Chris