The heart of Buddhism is the Four Noble Truths: the reality of suffering, the reality of desire, the goal of nirvana, and the solution of the eight-fold path. In the case of suffering and desire, Buddhism and Christianity agree that all of life is broken, and at the heart of that brokenness is human desire.
But they disagree in two important areas: first, the Buddhist goal of nirvana is an impersonal one – salvation in Buddhism is a matter of losing one’s identity and ceasing to exist; but for Christians, salvation is a redemption and repairing of the human person. And second, the path toward this salvation for Buddhism is a matter of doing good things (the eight-fold path); while for Christianity, salvation is purely a gift of God’s grace on behalf of Jesus. So at the heart of the difference is the resurrection of Jesus, who forgives and rescues the whole human being, spiritual and physical, and who gives us this salvation not based on anything we could do to earn it but purely as an act of his grace and mercy.