What is theosis?

Wondering how this compares to the Protestant idea of sanctification or any Catholic theology --- Nous response: Theosis, or deification, is the Orthodox Christian teaching that through God's grace, humans are transformed to share in the divine life, becoming by grace what God is by nature. This process is the ultimate purpose of salvation, initiated in baptism and nurtured through the sacramental life, prayer, and ascetic struggle. As St. Athanasius proclaimed, "God became man so that man might become god" (cf. 2 Pet. 1:4). The Holy Fathers unanimously affirm that theosis involves participation in the divine energies, not the essence, preserving the Creator-creature distinction while affirming true union with God.