Okay, I am new to calculus so can you guys just explain something to me. What is exactly are you doing to a function when you differentiate or take the derivative of it? I thought that when you do that, you make an instantaneous solution to where something is at all times with respect to the other axis. Is that correct? Also, whenever you see calculus in advanced physics, I don't understand. You can only use indefinite integrals and derivatives when you have a valid function right? So all these advanced physics problems need functions to go along with them right? Thank you guys!