I will use the term "device", if I want to refer rather loosely to something I can hold in my hand, or something depicted on a circuit diagram, aka schematic, or one of the "bits" provided for on a PCB design.
It isn't a term that you often see in any official KiCad material.
Beware, however: When I refer to a "device", I am probably speaking of something that will, in different contexts, need a "footprint" or a "schematic symbol". (schematic symbol are sometimes called "components", particularly in old documentation. If the latter, remember KiCad uses the term very narrowly, meaning only one of the schematic symbols for circuit diagrams.
Another use of "device" in KiCad
It will be one of the sources of schematic symbol on offer when you go to add a schematic symbol to a circuit diagram when using Eeschema.
Library names haven't given me trouble; I hope your experience will be the same.
As ever, if I am overlooking something (or Just Plain Wrong!), please write, so I can revise the information which was not clear to you, and thus save the next reader the nuisance you had?