Rules that say what you may and may not do with a service.
An AUP is the pool rules on the wall. Swim all you want. Do not cannonball onto someone or dump blue paint in the water.
Platforms use it to stop misuse. Break the rules, and you may lose access or face consequences.
AI-regulation
An AUP often turns AI-regulation into platform rules.
AI Guardrails
AI Guardrails can enforce some AUP limits in a product.
API
Many API services use an AUP to ban misuse and illegal calls.