A disaster is any event that halts business activity on a large scale. In most cases, we are thinking about natural disasters, but there are also man-made disasters and all of them can happen at any time without warning. Technologies and all IT services could be impacted by these kinds of disasters. Of course, there are other and more important aspects; like human life that can also be at risk, but for BC, we put the main focus on the business-critical services and applications.
DR provides BC in the event of a disaster, and may be just localized on equipment (like a single server) or globally on an entire site. Business will be recovered by following a specific DR plan; it is just a subset of the BCP. In the worst case of a disaster that impacts an entire site or region, usually, the recovery process uses a remote location called a disaster recovery site...