When does my employer coverage actually end? - what worked for you?

HR said my health plan continues for a bit and I do not understand how. There are 12 people counting on me, so I am trying to be careful. The letter is unclear about dental and vision. What should I do about appointments?

I moved my appointments earlier while coverage was active. It saved me a bill.

Dental and vision sometimes end on a different date from medical. Mine did.