These are the terms as I use them. May or may not be in line with how other people use or apply these terms (I am stubbornly set in my ways and won’t change)… YMMV.
Servitors are beings which are created through ritual work by the magician to carry out a specific task, ideally in the short-term, and are dissolved after they do their job. That’s, I think, fairly bog-standard for that term.
Fetches are parts of the magician’s own energy body which they can independently operate to Get Shit Done. Sort of like Astral Projection, but not on the astral so much as … y’know… sending one’s Fetch against an enemy to claw their eyes out as per accounts in the Witch Trials. Some folks use this term for basically what I mean by servitor, which I don’t get at all.
Fetishes are objects with power. Whether someone has empowered an object, or found an already powerful object. They can be containers, anchors, or houses for beings of both the pre-existing and created variety. I think some people use this term to mean aggregates of woo-woo curios that can obtain an almost-independent form or nascent intellect on par with a Servitor. I don’t.