What is a function call?

A function call refers to the execution of a previously defined function, allowing it to perform its designated task at that moment in the program. When you call a function, your code effectively tells the program that you would like to use the set of instructions contained within the function right then and there. The function can return a value, modifying the program's state or output based on the logic coded within it.

When considering the other options, declaring a function without executing would simply define the function but not execute its code; this does not meet the criteria for a function call. Creating a loop inside a function refers to a specific structure within the function's code and is not inherently about calling the function itself. Defining parameters involves establishing input values that the function can take, which is part of its definition rather than its execution. Thus, only executing a previously defined function accurately captures the essence of what a function call is.