What is CAP Theorem (CAP)?

As it relates to theoretical computer science, CAP theorem is a theory that was developed by computer scientist Eric Brewer that states that it is impossible for a distributed data network to at the same time provide more than 2 out of 3 guarantees: consistency, availability, and partition tolerance (which stands for the acronym CAP). The theory was used as the basis for the Blockchain Trilemma theory which states that it is impossible to build and operate a blockchain protocol that is: decentralized, scalable, and secure.