An envelope is a flat, usually rectangular or square, paper container designed to hold a letter, card, or document. typically made from lightweight paper, it is sealed by folding a flap and securing it with adhesive or a mechanical closure. envelopes come in various sizes and styles, including standard business envelopes, padded envelopes for added protection, and decorative envelopes for special occasions. they often feature a designated area for the recipient's address and postage. envelopes serve a crucial role in communication, offering privacy and protection for the contents during transit, and are widely used in personal, professional, and commercial contexts.