Hi @Onis_Csadi1, glad you are liking Grist!
Grist documents are individual SQLite databases, and attachments are stored within a table called _gristsys_Files within those individual databases. So when you click Download and get a .grist file, that contains all the attachments for that document also. And if you look at the volume mounted at /persist for a Grist container, there should be a docs directory with all the .grist files. There’s a list of the files and what they are for at Self-managed Grist - Grist Help Center
Storing attachments like this has the advantage of being self-contained, and makes it easy to back-up and restore a document. It does mean you are limited by disk space. We don’t yet have an option for storing attachments separately to the document that contains them.
If you hook up snapshot storage, then documents (with their attachments embedded in them) can be stored in S3 and similar. The steps are described in Self-managed Grist - Grist Help Center. I’d say it is worth setting this up early, for the peace of mind of having previous versions of documents available in the UI.