The concept of the Trinity really isn't that complicated, as Antonio describes. People only get into trouble when they understandably start analogizing it to other things. At the risk of doing precisely that, the closest I've heard is something like the three primary phases of water at the precise temperature-pressure triple point allowing solid, liquid, and gas to occur simultaneously; however, I'm not sure this quite works as I think the triple point lets all three phases occur in minute physical and temporal proximity to each other, not simultaneously for the exact same molecules (although I could be wrong), but it's not a far leap for the mind to imagine water doing exactly that under some infinitely improbable set of precise conditions: one molecule truly existing as all three phases simultaneously, each phase fully the molecule yet each distinct in attribute.
The Trinity may not be that complicated to accept as a belief, but modern Christians are frankly horrifically bad at talking about the Trinity and bad at convincing those with doubts/reservations about the Trinity.
