The Holy Trinity is the biblical, monotheistic doctrine of only one God in three distinct co-equal, co-eternal persons: The Father, The Son (Jesus Christ), and The Holy Spirit...three persons of one nature and being. The Father is not the Son. The Son is not the Spirit, and the Spirit is not the Father. Each of them is fully, equally, and simultaneously God.
While in no way can we human beings be considered divine, one way to understand the Trinity is to understand we are composed of three facets but housed in one being...body, mind, and spirit.
This candle is burned when we wish to commune with the Divine and ask for deeper understanding of self and our place in the Universe.