Continuous.

Instead of jumping from 1 to 2 to 3, we move smoothly across all (typically real) numbers. Obviously this would go to infinity almost every time because there are infinite real numbers between any two distinct real numbers. So instead, we merge it into a bunch of skinny rectangles with their bottom on the x axis and the top at the value of the function for the start of the rectangle. As we shrink the width of the rectangles, it approaches the continuous notion.

Continuous means “smooth” - there are no jumps Discrete means there are jump

Short answer: Imagine that the integer used in the for loop is a float instead.

Longer, a bit more precise answer: An integer can only have discrete values (i.e. -1, 0, 1, 2, …, 69, … etc.)

A real number (~float with infinite precision) can have an infinite amount of values between two discrete values.

An integral is, to put it simpy, a sum of all the results of taking those infinite values between two discrete values (an interval) and feeding them to the given function.

It’s a for loop over an infinite set of real numbers rather than over a finite set of integers => a non-discrete for loop