What he’s meaning to say is the circuits are either ON or OFF. Like electrical charges, there’s either NEGATIVE or POSITIVE, or with magnatism, there’s NORTH or SOUTH… that’s it. A computer runs on electricity, and with that, there are only two “states” that electricity can be in… either ON or OFF. Computers are not like the human brain that can handle multiple situations. Computers are dumber than garbage cans!!! The only decisions a computer can actually make is… is this circuit ON or OFF? And depending upon that decision, the next command is one thing or another… and so on down the line.

Hope this helps.

Computer are made of Transistors. To have a robust circuit transistors switch between 2 values. Max Voltage and Zero Voltage. Thus everything is based on having 2 states, unlike 10 different values in the decimal world.