In order to share content with another user, it is very helpful to package the file prior to sending it. This puts all of the images, fonts, styles and any links you might have all in one place, making it easy for the user to use the same file. Because you are not amble to embed images within InDesign, this makes it highly important to package files before sharing.
How to Package an InDesign File:
Illustrator is not as important with final files because you have the ability to embed links and outline fonts. However when sharing a file you would like to keep editable, this can be a very helpful tool.
How to Package an Illustrator File:
ZIP is an archive file format that supports lossless data compression. It can contain one or more files.
When to use a ZIP: When you need to send one or more large files over email, archive the files together by zipping.
How to Zip on Windows 10: