Knowledge Base + AI Model

When I’m using an AI Model to answer questions, does it use my knowledge base as a reference to direct its answers, or does it rely solely on the underlying LLM Model?

I’m asking because I need to use the AI Model cause I’m looking for some personalized answers based on the user’s inputs, but I got some learnings that I would like to put in the knowledge base to be used as a good practices by the AI.