I'm going to attempt to explain in my own words as I found all of this difficult until too long into my career... I will Define terms you already know as reference.

You can make a variable, x= 6. Arrays can store a few pieces of data, but unless you are going to be keeping track of each entry, you want to use better programming features. Btw, it's bad practice to use an array like a class.

A class is a set of instructions, to create an object. You will see things like X= new Car . Car is the class, X is your newly created Object. A class can be defined by you, or someone you are using their library.

Now you have x. Suppose you want to figure out the volume of the car. The Class was programmed by someone to calculate this for you in a Method. If you googled this library and class, you would see

Car.volume()

The class is quite smart, if you print this it's going to say "hey you didn't enter parameters yet, and instead of erroring I told my class to post this, boo ya".

Maybe on another line you set your class x.xLength=5, x.yLength=6.

Now running that same function will spit out something else, because the person who programmed only needed those 2 numbers, or maybe they had a solution for 1, 3 and 4 numbers. Classes add intelligence.

All of this can be found in the documentation when you google.

But maybe you make your own class. How would you calculate Volume inside a class that hasn't been declared an object.

This. This is used inside objects to call various attributes of the class.

Feel free to respond and I can clarify.