What is "Group and Save" in blood transfusion? Pl explain in details?

Its something related to when a doctor orders blood for his patient.

patients for whom the likelihood of blood transfusion is less than 30% do not have blood crossmatched but instead have their blood group established and their serum checked for antibodies. This "group and save" provision allows rapid blood delivery in an emergency.

A blood group involves mixing patient's cells with known anti-A, anti-B, anti-AB and anti-D antisera (forward group) and mixing patient's serum with known A, B and O cells (reverse group).
An antibody screen involves incubating patient's serum with (usually three different) screening cells that have been chosen because between them they carry all the common antigens that usually cause transfusion reactions. Some of these antigens are C,c,Cw,D,E,e,D,Kell,k,Fy(a),Fy(b),Jk(a),... and a few more. If a reaction occurs for example with Kell positive cells, then the patient can only receive Kell negative blood. Anytime someone has a blood transfusion (or women through pregnancy/childbirth) they are exposed to foreign antigens which can illicit an immune response. If you have a negative antibody screen there should be no problems getting compatible blood. If you have a positive antibody screen the antibody must be identified and units of blood that are negative for that antigen must be found before blood is issued.
These days, many laboratories around the world no longer actually crossmatch blood once the patient has been found to have a negative antibody screen. Group matched only blood is issued. If the patient has an antibody a full crossmatch must be performed.
I work in blood banking doing these tests.