1) Several folios collected together for sewing as part of the bookbinding process make up a signature. Multiple signatures usually make up a book. A single signature is much like a booklet but it takes several together to create the longer publication. The signature is formed from a printed sheet of paper that has been folded (in half, quarters, eighths, etc.) and cut, if necessary, to create a set of pages in proper order for reading.
2) A signature also refers to a letter or other character printed on the first page of a section of a book (each sheet that becomes a signature when folded) and used as a guide for collating and binding the book.
3) The contact information of an ad or other document or the credit line (such as on the back of a custom greeting card) is sometimes referred to as the signature, contact block, or credits. It generally consists of one or more of:
- Advertiser/Business Name
- Phone Number
- Map or Driving Directions
- Web Site Address
Outside of desktop publishing, signature has other meanings including a name written in one's own handwriting. For the purposes of this site — unless talking about a signature on a design contract — a signature refers to book pages, reference characters, or contact information as described above.