Liskov substitution principle

[George2]

Hello everyone,


I am learning Liskov substitution principle,

http://en.wikipedia.org/wiki/Liskov_substitution_principle

But the description is not common senses. Now I understand this principle to be, if we have some methods in base class, then we also need to implement the methods in derived class. My understanding correct? Anything else missing?


thanks in advance,
George