I guess it's access to Gemini, because that's the plan I'm on and you can access Gemini using gemini.google.com or their phone app (Android/iOS). I couldn't find information on the API, maybe it's on that page, but I couldn't find it from my phone browser. Anyway, I use OpenRouter pretty much, so I have no idea if the API is part of my plan.
https://knowledge.workspace.google.com/admin/getting-started...