What is the difference between classification and regression? I understand classification....a discrete response or category, like animal is dog or cat.

The author says..."Regression techniques predict continuous changes such as the change in temperature, power demand, or stock market prices."

I can't wrap my head around what he means.

Thanks.
For the sake of illustration, let's imagine that you're trying to predict the amount of gas in the tank of your car.

A classification problem statement of this question would be whether you have gas in your car (yes or no).

A regression statement of this problem would predict the level of gas in your car (anywhere between completely full or completely empty) and could take any value.

The output of a classification model can be one of n options, where n is the number of classes (and/or the probability associated with each class).

The output of a regression model is a (possibly bounded) continuous value.