Hello @jessy and welcome to Microsoft Q&A.
Sometimes the results are larger than is practical to send in one go. In these cases the results are batched or paginated. The results are broken up into pieces, and the continuation token is used to track where you are in getting the results.
Think of a bookmark in a book. The book is the results of your query, and each page in the book is a portion of the results. The continuation token is the bookmark used to keep track of which page is next to read.
For example on how to use the continuation token, please see:
https://learn.microsoft.com/en-us/powershell/module/az.storage/get-azdatalakegen2childitem?view=azps-5.2.0#example-3--list-items-recursively-from-a-filesystem-in-multiple-batches