A more thorough explanation:

A sigillum is a seal that is pressed onto wax. It is a way to show that something is official or authentic.

• When a king wanted to show that a document was important, he would put his sigillum on it. This way, everyone would know that it was real and not a fake.
• Lawyers use sigilla to seal important legal documents. This way, no one can change the document without breaking the seal.

These examples show how sigilla are used to make sure that important documents are not tampered with. By putting a seal on a document, it shows that it is official and authentic.