1) A function is basically just like a machine, with inputs and outputs where the output depends on the relationship with the input, for example, the relationship is to multiply by 5, so the input would be 5, but the output would be 25, and so on. The relationship is not always constant, and may vary in different cases.
2) The relationship between x and y is that y is constantly a variable of x while x is an independent variable.
This means that x is value that is changed while y is a value constantly dependent on x. In the case of a function, x is the input while y is the output.
3) All function a relation, but not all relations are functions.
Done by: Adil, Jonathan and Yu Tao