A closed quantum mechanical many-body system evolves unitarily. Therefore, in a strict sense, it should not equilibrate or thermalize. However, thermalization occurs, as it is revealed in experiments in ultra cold atom gases with very long coherence times. How do equilibration and thermalization occur then? Even if equilibration cannot happen at the level of the wave-function, it may happen in the expectation value of typical observables, as Von Neumann first pointed out. Recently, it has been understood that equilibration and thermalization are due to the typicality of Entanglement. In this talk, I will review some of the recent theoretical progress made in this field. Typically, quantum states are very entangled, and this implies that locally they look like thermal states. A long-standing problem is the meaning and role of integrability for thermalization. Recent novel results show that the structure of Entanglement reveals the connection between non-integrability, irreversibility, and thermalization. Finally, I will describe how some exotic states of matter also show exotic ways of equlibrating, which is very promising for quantum information processing.