The notation "f(c)" represents the value of a function f at a specific input c. In mathematics, a function is a rule that assigns each input exactly one output. For example, if f is a function that doubles its input, then f(3) would equal 6, since 3 doubled is 6. In this context, c can be any number or variable that the function f accepts. Understanding f(c) is essential in various fields, including calculus, algebra, and computer science, as it helps in analyzing how changes in input affect the output of a function.