What does it mean by buying TT or OD or selling TT or OD in foreign exchange?

When buying or selling foreign currency, "TT" stands for telegraphic transfer, which refers to electronic transfers of funds between banks. "OD" stands for on demand, which refers to transactions that are processed immediately. Buying TT means purchasing foreign currency through a telegraphic transfer, while selling TT means selling foreign currency through a telegraphic transfer. Buying OD means purchasing foreign currency for immediate delivery, while selling OD means selling foreign currency for immediate delivery.