A multi-file document usually contains several files, that is, files that together with the metadata constitute one multi-file document.
You can view the contents of a multi-file document by double-clicking it. In other words, a multi-file document is a fixed entity that contains several document files. For example, it is usually a good idea to include a proposal and its attachment in the same multi-file document.
Does your M-Files look different? - This video features the previous user interface. This video will be updated shortly to feature the latest version of M-Files (released in November 2022). Please note that the lessons in this video still apply.