According to the Mahayana Buddhist teaching of the trikaya, "three bodies," a Buddha is one with the Absolute but manifests in the relative world of form and appearances in order to work for the liberation of all beings. To accomplish this, it is said a buddha has three bodies, called dharmakaya, sambhogakaya and nirmanakaya.
The dharmakaya is the Absolute; the essence of the universe; the unity of all things and beings, unmanifested. The dharmakaya is beyond existence or nonexistence, and beyond concepts. The late Chogyam Trungpa called the dharmakaya "the basis of the original unbornness."
It is important to understand that the dharmakaya is not like heaven, or somewhere we go when we die or "get enlightened." It is the basis of all existence, including you. It is also the spiritual body or "truth body" of all buddhas.