Here are the parts you need for every kit

There are 4 basic types of kits that are sold on 1upkeyboards and they represent the kits that are sold everywhere.

This type of kit is like the Sweet 16 and Super 16 kits sold on 1upkeyboards. These are a very basic kit, but they help us to understand what is really required at the most basic level of a kit.

PCB
Controller
Diodes
Switches
Keycaps
Standoffs (or something to stop it from resting on the table)

So let's go down the list and explain what everything is, and what it does.

PCB - this is the circuitry for the keyboard, and links together the controller and the switches.
Controller - this is where the chip lives. The chip sees the signal from the switch and translates that into something the computer can understand.
Diodes - this is a semi-conductor that makes sure the flow of current is only in one direction
Switches - CherryMX, Gateron, clicky, quiet… the switch gives the keyboard its character.
Keycaps - gives your fingers something nice to rest on.
Standoffs (or something to stop it from resting on the table) - does exactly that.

Now that you know how these barebone kits work, you'll be able to much more easily understand the components that go into every keyboard kit there is.

Sandwich or Skeleton kits