The difference between invitations, invitations and invitations.

Invitation cards are intuitive, you can directly see the content, flat, and some materials are thick, just like prepaid cards, but the size is uncertain; Invitations used to be packed in wooden cases or boxes, but now they are packed in envelopes. Like letters and documents, they are sealed and generally accepted by the invited person, and others can't see the contents inside. Invitation cards are usually separated, such as greeting cards and wedding cards. They are not sealed, but they cannot be seen directly. They need to be opened like books to see the content.