What does the term "realization" in accounting mean?

Realization is also known in accounting as a "Revenue Recognition Principle".

So, means this is related to recognition of revenue.

Under this Concept, revenue should be recognized when the risks and rewards are transferred to the party, even not received the money.

I AGREE WITH MR RAMZAN  ANSWER 

Clearing your sales bills and crediting the proceeds in your account. Or receipt of Collection proceeds. Or revenue earned....Your choice.