A function is denoted by the function’s name followed by parentheses which contain the input to the function. The function’s implementation is sometimes explicitly statement by using the equals symbol.
The input to a function is referred to by many names: parameters, variables, and arguments. Functions often have multiple inputs deliniated by a comma.
A function takes input and produces output. The idea is a useful way to abstract away complexity and, especially in the age of computers, is a practical tool to solve problems.