Everybody/everyone – Every person in a group.
Everybody was angry about the film.
Everyone wanted to go to the park.
Everybody and everyone are essentially the same except for the fact that you are likely to hear everybody more in speech.
Somebody/someone – One person who is not being named or distinguished in any way.
Somebody has spilled my drink but I don’t know who it was.
Someone needs to come with me to the doctor.
Again, someone and somebody are interchangeable and the choice of which to use just depends on what helps the sentence to flow better when the word is inserted.
