The term "reserve" has several meanings depending on its context.
1) In finance, reserve refers to an amount of money set aside for a specific purpose or kept in reserve as a precaution against potential losses or emergencies. It can also refer to the funds that are held by central banks and used to back their currencies.
2) In military terms, reserve refers to troops or equipment that is not currently engaged in combat but is available for deployment if needed.
3) In a social context, reserve may mean holding something back, such as emotions or opinions, due to shyness, caution or self-control. It can also refer to keeping something in reserve, such as money or resources that are set aside for future use.