For example, the Catholic Church, including the Latin Rite, teaches theosis, although traditional we use the term deification instead (theosis is a Greek langauge word, deification is a Latin one). For example, here is my favorite passage of Docter of the Church and Thomist St. John of the Cross:
In order that both these things may be the better understood, let us make a comparison. A ray of sunlight is striking a window. If the window is in any way stained or misty, the sun’s ray will be unable to illumine it and transform it into its own light, totally, as it would if it were clean of all these things, and pure; but it will illumine it to a lesser degree, in proportion as it is less free from those mists and stains; and will do so to a greater degree, in proportion as it is cleaner from them, and this will not be because of the sun’s ray, but because of itself; so much so that, if it be wholly pure and clean, the ray of sunlight will transform it and illumine it in such wise that it will itself seem to be a ray and will give the same light as the ray. Although in reality the window has a nature distinct from that of the ray itself, however much it may resemble it, yet we may say that that window is a ray of the sun or is light by participation. And the soul is like this window, whereupon is ever beating (or, to express it better, wherein is ever dwelling) this Divine light of the Being of God according to nature, which we have described.
In thus allowing God to work in it, the soul (having rid itself of every mist and stain of the creatures, which consists in having its will perfectly united with that of God, for to love is to labour to detach and strip itself for God’s sake of all that is not God) is at once illumined and transformed in God, and God communicates to it His supernatural Being, in such wise that it appears to be God Himself, and has all that God Himself has. And this union comes to pass when God grants the soul this supernatural favour, that all the things of God and the soul are one in participant transformation; and the soul seems to be God rather than a soul, and is indeed God by participation; although it is true that its natural being, though thus transformed, is as distinct from the Being of God as it was before, even as the window has likewise a nature distinct from that of the ray, though the ray gives it brightness (The Ascent of Mt. Carmel).
I don’t think you can find a better explanation of theosis out there