Think back before the time of digital printing and photography. Imagine you wanted to make a portrait of your child and share it with others. One option would be to hand-draw a photo for Grandma. Then hand-draw one for Grandpa. Then one for Aunt Becky. You can see that this could take quite a lot of time!
The other option would be to find a way to make a print. You might carve the image into a flat piece of wood. Now you could soak that wood in ink, just like a stamp, and press it onto paper. Voila! An image! Press again onto a fresh sheet and you get another image. Suddenly you could make multiple copies of the image, all based on that one original. This is printmaking.
It takes a while to make that initial image, carving it in stone or wood or whatever you choose. Copper etchings are another common way to make these images. Once that image is carved and done, you're set. Now you can "print off" thousands of copies, one by one, and distribute those.
Each individal print from that engraved surface is called a "monoprint". It is one print from the carved design. Note that the carved design can be inked in a bunch of different ways. So you could carve a cat into wood, for example. You could then make a green cat using green ink. Wash the wood. Make a blue cat using blue ink. Wash the wood. Make a yellow cat, and so on. So even though you are working from one base design, you can still make variations by changing how you use the ink on it.
Where a monoprint is repeatable, a monotype is a one-off, wholly unique print. There is no mark at all on the base surface. None. It is completely smooth. It can be a piece of glass, a piece of metal, a tray of gelatin, you name it. That surface is smooth. You paint on that surface with various colors and make designs in it with stamps and such. When you are ready, you press your paper down onto the inky surface. When you lift off the paper, it now has ink on it in various shapes. Voila, done. You can never make that same design again. Even if you pressed another piece of paper onto the surface, now it has less ink on it and is going to make a different image - a "ghost print".
Here are my pages on printmaking, monoprints, and monotypes!
Randy LeSage Demo on Printmaking
Gelli Plate Printing - basics
Gelli Plate Printing by Joan Bess - book review
A Gelli Printing Adventure by Zehra Husain - book review
Lisa Shea Prints - Session 1 Large