FAQ: Higher-Order Functions - Functions as Data

I am having issues understanding how to utilize this for anything else later. I have searched around for examples of other small projects to try to wrap my brain around how this is useful, but this is the first topic they have covered where I cant even brain storm up my own idea on how to use it. There are not even really any tutorials on YouTube or anything. Unless you were doing some calculus here, I just don’t get it.