If you see something in your [EQUIPMENT](/help/commands/equipment/) list that has "covered" by it, it
means just that: you have another piece of equipment covering it. I.e., 
gloves cover rings on your fingers. People looking at you can't see items 
that are covered.

Humming and glowing equipment mean exactly what they say, too. The 
equipment hums (makes a vibrating noise) or glows with a faint light 
(not enough to see by, but enough to be seen in the dark).