Final answer:
Sealer in history refers to the ancient seals used by civilizations like the Indus Valley civilization. These seals, made from clay, depicted animals and an undeciphered script. They were used for various purposes and provide valuable insights into ancient cultures.
Step-by-step explanation:
In history, sealer refers to a type of seal used by ancient civilizations. One example is the Indus Valley seal from the Indus Valley civilization, which typically depicted animals and an undeciphered script. These seals were made from clay and used for various purposes such as marking ownership or authenticity. Today, we can study these ancient seals to learn about the cultures that created them.