A framework agreement is a contract between one or more buyers and one or more suppliers that sets the terms for future purchases over a set period. Rather than awarding a single job, it establishes who may supply and on what terms, with specific orders ('call-offs') placed later.
Frameworks are used when a buyer expects repeated or ongoing needs. Being appointed to a framework does not guarantee work, but it makes you eligible for call-offs during its term, which may run several years. Call-offs are awarded either directly or through a mini-competition among framework suppliers.