A class is an organized store-house in object-oriented programming that gives coherent functional abilities to a group of related code. It is the definition of an object, made up of software code. Using classes, we may wrap data and behavior together (Encapsulation). We may define classes in terms of classes (Inheritance). We can also override the behavior of a class using an alternate behavior (Polymorphism).
A Base Class is a class that is inherited by another class. In .NET, a class may inherit from only one class.