TOPIC: What is a MSA Master Services Agreement?

What is a MSA Master Services Agreement? It has one sentence in the PMBok but it doesn't say what it is yet it was in the prepcast which means it might be on the exam.

An MSA is a form of top level contract document that other contracts will attach to. For example, my company executes MSAs with our vendors and customers that detail what the relationship is, payment terms, discounts, corporate policies, termination, litigation, force majeure, etc. The document doesn't go into a detailed scope of any work to be performed. As services are offered, or projects are formed, the MSA will be amended by a Services Addendum or SOW that details the specifics (who, what, when, where) of what work will be performed. By having an MSA that everyone has already agreed to, you don't have to repeat common terms in every subsidiary contract. Those contracts assume the terms from the master. It makes negotiating contracts for specific contracts for services and projects must faster.