Backdoor is an independent program which has two components i।e. Server and Remote. Server component is installed on the victim system and remote component is the tool to control the victim system remotely. This is basically used for the hacking.
What is Adware and Joke or Prank?
A program that secretly gather personal information through the Internet and relay it back to another computer, generally for advertising purpose. This is often accomplished by tracking information related to Internet browser usage or habits.
A program that change or interrupt the normal behavior of your computer, creating a general distraction or nuisance.