Look.., in terms of agreements.., benefits and duties of each party involved.., if we agreed on you getting to enjoy my apples.., and me having to give you apples.., and me getting to enjoy your oranges and you having to give me oranges.., then that's what we agreed on.., either explicitly.., or implied..
(Implied contracts take place every day btw: You look at a pack of gum.., look at the $1 price.., show it to the store manager.., give him $1.., and walk outside.., you just executed an implied contract)