The notation "f ∘ g" represents the composition of two functions, f and g. This means that you first apply the function g to an input value, and then take the result and apply the function f to it. In simpler terms, you are chaining the functions together, where the output of g becomes the input for f. For example, if g takes a number and adds 2, and f multiplies a number by 3, then "f ∘ g" means you first add 2 to your number and then multiply the result by 3. This process allows for more complex operations by combining simpler functions.