On its own, a computer isn't very smart.
A computer is essentially just a big bunch of small electronic switches that are either on or off. By setting different combinations of these switches, you can make the computer do something, for example, display something on the screen or make a sound. That's what programming is at its most basic—telling a computer what to do.
Of course, understanding which combination of switches will make the computer do what you want would be a difficult task—that's where programming languages come in.
People express themselves using a language that has many words. Computers use a simple language that consists of only 1s and 0s, with a 1 meaning "on" and a 0 meaning "off." Trying to talk to a computer in its own language would be like trying to talk to your friends by using Morse code—it can be done, but why would you?
A programming language acts as a translator between you and the computer. Rather than learning the computer's native language (known as machine language), you can use a programming language to instruct the computer in a way that is easier to learn and understand.
A specialized program known as a compiler takes the instructions written in the programming language and converts them to machine language. This means that as a programmer, you don't have to understand what the computer is doing or how it does it. You just have to understand how the programming language works.