I got an email from Google Cloud on my work account "excited to introduce you to Gemini Enterprise".
Once I signed up, it said, "you have 30 days to try Gemini Enterprise – Business edition at no cost." After that, it costs US $21/user/month, which I can subscribe to here.
The main differences from Gemini Pro (consumer accounts) seem to be:
But if you're using Gemini via your Google Workspace account (i.e. your work account already has Pro subscription), then it makes no difference - it's all the same.
So I have no clue why Google's mailed me to buy the same product I already have.