Envelopes are used for a variety of purposes, including mailing letters, sending invitations, and storing documents. There are many different types of envelopes available, each designed for a specific purpose. Some of the most common types include business envelopes, personal envelopes, and invitation envelopes. Business envelopes are typically made from a heavier paper and have a professional appearance. Personal envelopes are made from a lighter paper and are often used for sending personal letters or notes. Invitation envelopes are typically made from a decorative paper and are used for sending invitations to special events.