A more thorough explanation:

An erratum is a mistake that needs to be corrected. It comes from the Latin word "error".

For example, if a book has a typo in it, the publisher might issue an erratum to let readers know about the mistake and how it can be corrected. Another example is when a scientific paper has an error in the data, the author might issue an erratum to correct the mistake.

Errata is the plural form of erratum. It means there are multiple mistakes that need to be corrected.

Overall, erratum is a way to acknowledge and fix mistakes in various forms of media.