Envelope can serve several purposes, depending on the context:

1. Communication: It's commonly used to enclose letters or documents for mailing, ensuring their protection and confidentiality.
2. Formality: It adds a formal touch to invitations, announcements, or business correspondence, providing a neat and organized presentation.
3. Containment: Used for storing important documents, receipts, or small items safely.
4. Symbolism: In ceremonies or events, envelopes often symbolize confidentiality, surprise (like in the case of awards or gifts), or official communication.

If you meant "envelope" as a metaphorical or symbolic concept, it could also refer to something that wraps or contains an idea, plan, or proposal, much like a physical envelope contains letters.