Creator is the IPTC Core name for the person who made the image, usually the photographer. The main copy is XMP dc:creator. IPTC By-line (dataset 2:80) is the legacy copy and EXIF Artist a third place for the same name. Google lists Creator among the photo metadata fields it extracts for Google Images.
An ordered list, not a string
Dublin Core allows several creators, so dc:creator is an rdf:Seq, an ordered array whose first entry is the primary creator. This is what ExifTool writes for two names:
<dc:creator>
<rdf:Seq>
<rdf:li>Jane Doe</rdf:li>
<rdf:li>John Roe</rdf:li>
</rdf:Seq>
</dc:creator>Read back, both standards look like this:
[XMP-dc] Creator : Jane Doe, John Roe
[IPTC] By-line : Jane Doe, John RoeThe comma is ExifTool joining list items for display. It is not in the file. A name written as "Doe, Jane" is impossible to tell apart from two people in that output, so read lists with -j (JSON gives ["Jane Doe","John Roe"]) or a custom -sep. To write a list, repeat the option: exiftool -XMP-dc:Creator="Jane Doe" -XMP-dc:Creator="John Roe" photo.jpg. Use += to append to an existing list.
By-line is repeatable as well, one dataset per name, but each dataset is capped at 32 bytes. ExifTool truncates longer values with a minor warning unless you pass -m. Keep it to the person's name; an agency or client belongs in the credit line.
Format support
XMP travels in almost every format that carries metadata. IPTC IIM does not: PNG has no standard place for it, so at best dc:creator and EXIF Artist survive a PNG export. That is one reason to treat the XMP copy as the reference and the others as mirrors.
Editing it here
XMP:Creator and IPTC:By-line are both in our whitelist, so the metadata editor shows and writes them on JPEG and TIFF. Its text fields reject commas and semicolons; enter a single name such as Jane Doe, and use ExifTool when you need several creators in order. The EXIF vs IPTC vs XMP guide explains why one name ends up stored three times.