I spent an hour after working trying to explain the concept of the trinity to a friend of mine who is a Jehovah's Witness. At one point I used an analogy of a man traveling through time to meet an earlier version of himself, and then a third version showing up. By the end of the conversation I had almost convinced myself, let alone him.
In conclusion there is the father, Jehovah..big "G" God. Next there is an aspect of himself he created called the Holy Ghost. This he uses to converse with mortal man. Third there is Jesus, an aspect of himself created to fulfill the Mosiac covenant, redeem mankind and create the new covenant.
Like the time traveller meeting two earlier versions of himself, all three are at once individuals and at the same time one being. It's an inexact analogy, but it suffices.