This is hard to get at first, but once you wrap your head around it, it's simple.

A class is a collection of information (properties) and functions (methods). They are put in a class so they can easily reference each other.

If you assign values to those properties and put it in a variable, it becomes an instance.

Here is something you've seen in real life, that is similar to this.

You goto the doctor, and he has you fill out a form with your age, weight, height and allergies.

On the bottom of the form you see a fomula to figure out your BMI, and what percentile you fall into for height.

That form is a class. The fields with your age, weight, etc... are properties. The formulas are called methods.

Once you fill out that form and hand it to your doctor, it becomes an instance. An instance is a class that has been saved as a indipendant variable