Guidelines
Guidance, eg. a brand manual & tone of voice
Guidelines are the shared agreement that keeps a brand coherent as it grows.
Brand guidelines are the documentation of how the brand should look, sound, and behave across different contexts. They cover visual elements (logo usage, colors, typography, imagery), verbal elements (voice, tone, key messages), and often behavioral elements (values in action, customer experience principles). They exist so that the brand can be represented well by many different people, across many different situations, without requiring a central decision-maker every time.
The failure mode for brand guidelines is making them too comprehensive and then never using them. A 200-page brand bible that lives on a server is worth far less than a clear, practical 20-page guide that people actually consult. Guidelines should be written for the people who will use them, not to demonstrate how thorough the brand strategy process was.