There has never been an understanding of the Holy Trinity accepted by all of Christianity. The words may be the same, but their meanings are different. And a number of churches centered in the ministry of Jesus Christ do not accept the idea of the Holy Trinity at all. (This would include Unitarians, United Church of Christ, and Jehovah's Witnesses, among others.)
The basic Unity understanding, from the teachings of cofounder Charles Fillmore, equates the Trinity of Father, Son, and Holy Ghost with a metaphysical trinity of Mind, Idea, and Expression. This describes the process of creation by which the Allness of Divine Mind expresses as the Christ—the fully divine nature, fully God Self that Jesus taught and demonstrated as his true nature, and the true nature of each of us. As the Christ, we bring the divine Ideas emanating from Divine Mind into expression through the choices we make.
Mind, Idea, Expression. I may not be explaining it clearly; I might see it differently tomorrow, but nothing can change the universal Truth of a divine Presence and Power moving through us as the Christ to bring into manifestation, choice by choice, the new dimension of life that Jesus Christ calls "the kingdom of heaven."
It is certainly possible to embrace this holy trinity of mind, idea, expression on any spiritual path that recognizes it, whatever terms we may use, whatever teacher of Truth we may follow. And we create "God's kingdom" choice by loving choice. It will come into full expression when we come together in spiritual consciousness to lovingly dissolve the negative energies that cloud our understanding of our true Identity.