The way current computers work is that they use electricity to process information. Modern computers only use 2 states. Either no electricity is flowing (0) or there is electricity (1). This might sound complicated but it’s pretty easy. Think of a lamp. If you turn the switch off no current is flowing and the lamp is off. This represents a 0. Vica versa, opening the switch allows current to flow and the lamp turns on. This would be a 1.
You can use these 1’s and 0’s to do simple logic. For example, imagine a lamp with 2 switches along the cord. The lamp will only turn on when both switches are closed. This represents a logical AND gate. Swap the switches for electronic transistors and this is all your computer is doing. You can combine logic gates to make a circuit that can add binary numbers together, or a bit of memory, or a control unit. With a complicated enough set of logic gates you can do all sorts of math, render video, etc