The expression "f(g(x))" represents a composition of two functions, where the output of one function becomes the input for another. Here, g(x) is the first function that takes an input x and produces an output. This output is then fed into the second function, f, which processes it further to give the final result. In simpler terms, you can think of g as a machine that transforms x into something new, and then f as another machine that takes that new thing and changes it again. This process allows us to combine functions to create more complex relationships and outputs.