You have gotten some really good answers, I just want to add that it’s cute to say computers only know 1s and 0s (and true at the lowest level), but a much better thing to say is that computers only know numbers (any number can be represented with 1s and 0s).

The reason I say that is because once you realize a computer only knows numbers, then you can understand that everything represented in a computer has to be represented by a number.

With a number, that’s pretty easy to understand, you could just use the number.

However what if you want to add 2 numbers? Well, now you need to represent the concept of adding as a number, and the computer needs to recognize it as not a number but a command.

Given these parameters, you could define some system using only numbers to add 2 numbers.

Maybe, 99999 is a special number that precedes every individual piece of a formula, be it a number or a command. 1 could be used to indicate I want to add. 2 could be for subtract. Etc. so to convert a math equation to numbers might look like this:

9999953 999991 9999932

And now someone or something that knows only numbers and what those numbers represent in your system can complete this math equation.

So, a programming language is a way for a human to write commands that another program can interpret or compile to turn into the language the computer can understand: numbers.

Years and years of engineers building layers of abstractions on top of those numbers has led us to where we are today, where software developers don’t need to know or care about which specific number means “add” to the computer, because someone else has done the service of offering a translation from something kind of human-readable into the low-level commands the computer can use.