Tutorial or reference on metadata fields for document and image files?

[AES]

When I look at the metadata fields (I'm assuming that's the appropriate
term) which can be associated with an image or document that I catalog
into iView MediaPro (my image and document cataloging tool of choice), I
see that the dropdown menu for "Fields" in iVIew has three submenus:

Media Info (about 4 dozen named fields)
Photo EXIF (about 3 dozen named fields)
Annotations (maybe 4 dozen more named fields)

Also, when I look at the Sort menu for an iView catalog I see a lengthy
choice of "Sort By" options which seems to have some (but not total)
overlap with the field names in these lists of Fields. So:

Q1: Can anyone suggest a good (but not too detailed) tutorial or
summary or overview of these metadata fields and what sort of file types
will support each of them within the file? (I don't really know which
of these fields are inherently associated with various file types as
part of their standards, and which may be just custom fields used and
maintained within the iView catalog).

Q2: Actually, I don't really care about most of these fields: all I
really want to do is to identify two or three fields in the above lists
that will for sure be present and supported in all of the file types
that I happen to use, which is basically just

PDF, RTF, TXT, JPEG, GIF (Animated GIF), TIFF, and PICT (Picture)

so that I can then use these fields for my own purposes -- which are
basically to have two or three "comment" fields which I can stick
various personal comments and annotations, and a couple more where I can
stick "sorting" terms or numbers that allow me to make custom sorts.

Anyone have any suggestions for these fields?