Offset screwdrivers or screwdrivers are normal screwdrivers in all formats (slotted, Phillips, Allen...) with one exception: they are angled.
Sometimes you just can't reach the screws at certain angles, which is where an offset screwdriver can help you.
Angled screws are - as the name suggests - angled screws. Usually one of the angles of the screw has no thread and serves a certain function. For example, as a hook/part holder for tools and other work materials.