1. The signature of the author is the name left by the author, just as you usually sign your name after painting.
2. Identification seal: it was left by contemporary or future generations when they collected and appreciated, for many reasons, some friends and scholars drew money from each other to show friendship, and some collectors left their own collected marks when they collected historical sites, which are also the basis for future generations' identification.
3. Seal stamped at the place where the paper seam meets, which is used to prevent someone from taking the opportunity to forge.