There is no need for confusion - the two words in each pair have exactly the same meaning and use.
Some people say that the '..one' versions are more formal, but in practice there is no real difference. You can use whichever word you prefer in any situation.
someone = somebody
everyone = everybody
anyone = anybody
Native speakers use both in speech and writing interchangeably. Some people naturally prefer one option. Others use them both without thinking why they choose one and not the other in a particular situation. So you can relax!