My question is how to explain the Holy Trinity and who the Father, Son and Holy Spirit is to someone who is not Christian.
We do not claim to be able to explain the Trinity to ourselves, much less to others. God is infinite. He cannot be explained fully to the human mind.
We know from scripture that God is one. We also know from scripture that there are three distinct persons who are God, the Father, the Son, and the Holy Spirit. We say that there is one nature in God but three distinct persons. This is unfathomable to us.
What makes it unfathomable is that, in the world we know, there is indeed one human nature and millions of persons, but these persons are both distinct and different. In God the three persons are both distinct and identical. There is nothing in one missing from the other.
The way to the Father is through Jesus Christ. It is by presenting Jesus Christ, God, Man, who died and resurrected that we can attract non-Christians.
We can however, ILLUSTRATE the Trinity. St Patrick used the shamrock. One shamrock, three distinct lobes.
The Trinity cannot be compared to an addition (1+1+1) but to a multiplication (1 X 1 X 1).
Another illustration, often used, is the triangle, whose sides are distinct but inseparable one from the other.
Our human thought process can be used as an illustration of the Trinity : mind, ideas, words. Different, but simultaneous.
Finally, we have St.Augustine’s analogy of a lover and a beloved. God is love. There has to be a lover, a beloved and a relationship of love ; these represent the Father, the Son and the Holy Spirit.