Envelop means (As a verb) to wrap around; to cover completely; to conceal, to hide: “People envelop themselves in problems because of their own stupidities.”
Envelope means (As a noun) a cover or a paper wrapper holder for a letter: “Envelopes are the devices that carry the message of the lover to the loved.”
She first decided to envelop the lovely card she was sending to her mother in pink paper before she put it in the envelope to be mailed.