What is the meaning of the term “Genocide” as opposed to “Crimes against Humanity”? [closed]

Genocide as a term came into being relatively after World War 2. There used to be a term earlier called Crimes against Humanity which used to be used to describe similar events. This use of this term has decreased over a period of time and the term Genocide is used increasingly in modern political parlance.

• What political forces shaped the usage of both these terms?
• Did the definition of fundamental Human Rights have anything to do with this?