How were seals used ? what information do they provide about harrapan civilation?

How were seals used? what information do they provide about harrapan civilisation?

Seals were used for facilitating long-distance communication. When a bag of goods was transported, its mouth was tied with a rope and wet clay with one or more seals being pressed to leave an impression. This ensured that the bag has not been meddled with.
The Harappan seals found in West Asia show that the Harappans traded with West Asian countries.