Customized versions of Gemini within the Gemini app (expanded in Google AI Pro, formerly Gemini Advanced), configured with specific instructions, context, and tone for a recurring role or task (e.g. a "Gem" that is an expert in contract review), without needing to rewrite the prompt each time.
In GENAI-L (Domain 2, section 2.2) it appears as a feature of the Gemini app aimed at end users who want a personalized assistant without building a full agent in Agent Platform.
Gems is a concept that can show up on the exam. Check the full guide to see it in context.