They are described in build mode.
Base game: environment 5
Seasons & Generations: environment 4
Late Night: romantic decor 4
Pets & Island Paradise: playful decor 4
World Adventures &Showtime: confident decor 4
University & Into the Future: focusing decor 4
Ambitions & Supernatural: inspiring decor
Having one in the room was enough to bump my sims into an inspired, focused or flirty mood. The moodlet they give is only +1, so if your sim is strongly into another mood they aren't enough to overcome it. However, if you are fine or happy they are enough to get you into the mood you choose.
As well as enabling and disabling mood auras, you can change the colour and intensity of the light emitted (the lamp itself remains it's original colour, but is effected by the light passing through it).
I've put an inspiring lamp in the bedroom, and unless my creative sim wakes up with low needs, she wakes up inspired.
Jess