A government contracting officer can use many different contract types. A few examples are listed below.
Definitive Contract: This contract type is used for a Specific one-time Scope and Price.
IDIQ: Indefinite Delivery/Indefinite Quantity contract - if and how much a contracting officer awards you work is not determined. It is just a placeholder. Think of it this way - you can enter the room but you don't have a seat at the table yet or you have a garage (IDIQ contract) but not a car (work) yet.
OASIS: One Acquisition Solution for Integrated Services (OASIS)
STARS: The 8(a) Streamlined Technology Acquisition Resource for Services (STARS)
CIO-SP: The Chief Information Officer-Solutions and Partners
NASA SEWP: The NASA SEWP (Solutions for Enterprise-Wide Procurement)
Additionally, there are firm-fixed price (FFP) where price is fixed, Time & Materials (T&M) based on labor hours and expenses, and Cost type contracts requiring more compliance.