Object Oriented Programming is pretty simple in concept.
If you look at the world abstractly, everything belongs to one 'class' or another. Ford Mustang, Dodge Caravan, Ford F-150, BMW X5. If you wanted to pick a generic class to include all these four things, you'd pick "vehicles" - they're not even all classified as cars, technically. Each of these 4 'instances' of vehicles are certain similarities, like they all have tires, all need maintainance after X distance traveled, all have a certain body colour - those will all be variables belonging to the class "vehicles" itself. There are also certain things like checking the oil, filling up with fuel, etc. that you carry out for any vehicle - these are class methods. In this method of setting up your code you have a centralized place in which all of your code is defined rather than repeating those variables and methods for each vehicle separately. As you'll find out when you inevitably go hunting through long pieces of code for a single variable reference or two you'll bless the concept of centralization!
Java and C++ are OO languages by design. Pascal, C and other languages aren't natively OO but if you think about it, you can always structure the way your variables are set up to assume object-oriented form. I actually like to think of object-oriented as class-oriented, it brings across the idea of centralization of code in classes more directly.
For small pieces of code, OO tends to get in the way - why define a base class if you're only going to have one object or two? Well, that's for modularity and in the case you someday want to reuse that code in a larger fashion or someone wants to tack more objects into your code at a later date. A lot of professors froth at the mouth when talking about abstraction and OOP as a gift from God, that's just senility setting in. Remember not to pay TOO much attention to the buzz words your teacher uses (abstraction, modularity, metaclassing) and you'll be fine. Professors have a way of trying to make everything seem complicated.