Object-Oriented Programming: Objects and Classes
The first in a few videos specifically on the OOP paradigm. This introduces the core concepts of classes and objects, and the attributes and behaviours (and other synonymous terms like fields, methods, subroutines, etc).
This video and the next few are coming at this topic from a more theoretical perspective. Throughout, I'd suggest you try and understand how to implement these techniques in your own language (which may have its own subtle differences and nuances).