Data is often used to represent concepts, objects & systems in the real world. Computers represent everything (i.e. both data and instructions) as sequences of bits (short for binary digit), whose values (like a toggle switch) can be either on or off; we use off to represent 0 and on to represent 1. We can group these bits into larger and more complex structures to represent anything else.
The easiest things to represent are dichotomies (e.g. true/false, yes/no, up/down, north/south, etc.) because it takes only a single bit to represent them. We call these booleans (in honour of George Boole, a British Mathematician & Philosopher).
Next up are numbers.