A blood bank is a center where blood gathered as a result of blood donation is stored and preserved for later use in blood transfusion. The term "blood bank" typically refers to a division of a hospital where the storage of blood product occurs and where proper testing is performed (to reduce the risk of transfusion related adverse events). However, it sometimes refers to a collection center, and indeed some hospitals also perform collection.
During emergencies, a patient can get blood from blood banks which is subject to availability of a particular blood group. In case required blood is available in a particular blood bank, the blood is given to the patient through a replacement donor who may be a friend or relative of the patient.
In case, the particular group of blood is not available, there are many voluntary blood donation organizations who may arrange that particular group of blood through voluntary blood donation.