That sentence had a lot in it, and deserves some more explanation…
There are many different programming languages, all with their own strengths and weaknesses, but they fundamentally all do the same job of letting the programmer express instructions for some behaviour. They have to do this in a precise-enough way that the computer can actually follow them.
Compare this to some other languages we have seen for computers: HTML and CSS. Both of those are computer “languages” but they are not programming languages since they aren't used to create programs. (They are a document markup language and a visual style language, respectively.)
Behaviour on Web Pages