It depends on the file type. Check the column for the type you have.

PS. Non-standard means it is stored but other players might not read them the same way.

I found a table which compares the different file formats with respect to their tag compatibility. It does not explicitly mention which tags are stored solely in the DB but I suppose if there is a full row of "No"'s for each file format this would be a DB only tag. There are only two such tags:

1. Times Played
2. Related Library Entry

Ok, I think that answers my question. Sorry for the RTFM.

Yep, check the help file in MM. It contains a list of tags and where they are stored.

You'll loose some information when you loose the DB.

Can anyone shed some light on which song properties are stored in some song tags and which ones are only stored into the database?

In other words, if the DB is lost due to some circumstances, can everything be retrieved from the song tags alone? Or which info would be lost forever... I am especially interested into the classification and rating properties. How "standard" are these?