I have some basic questions from calculus

Can someone please clear that for me ?

I am not good at mathematics , before i even attempt to learn calculus properly .

I need to get some clarity about a few basic things .

What exactly is a function ?

for example ,

y=5x+6

In that equation ,

Quote:

Most times you see an equation, the dependent variable will be isolated on one side. The independent variable is usually designated by *x*. The dependent variable is typically designated by *y*. However, any variables could be used in place of *x* or *y*. In the equation below the dependent variable is *y*

Quote:

Independent variables (inputs) are fed into your machine (i.e. your formula) to see what the output is (i.e. what the values of your dependent variables are)

Is calculus about the relationship between the two different unknown's in an y x graph ?