A set of guidelines like coding standards , test-data handling , object repository treatment etc... which when followed during automation scripting produce beneficial outcomes like increase code re-usage , higher portability , reduced script maintenance cost etc. Mind you these are just guidelines and not rules; they are not mandatory and you can still script without following the guidelines. But you will miss out on the advantages of having a Framework.
A “Test Automation Framework” is scaffolding that is laid to provide an execution environment for the automation test scripts. The framework provides the user with various benefits that helps them to develop, execute and report the automation test scripts efficiently. It is more like a system that has created specifically to automate our tests.