How would you describe calculus in simple terms? I keep hearing about this weird type of math called calculus. I only have experience with geometry and algebra. Can you try to explain what it is to me?

Calculus is a field which deals with two seemingly unrelated things.
(1) the area beneath a graph and the x-axis.
(2) the slope (or gradient) of a curve at different points.
Part (1) is also called 'integration' and 'anti-differentiation', and part (2) is called 'differentiation'.
