Elemental motes are elemental fragments which can be assembled into primal ingredients, used in many professions (at the Master level).
There are multiple ways of collecting each mote type which vary by element, but all of them drop off of certain Outland mobs related to their element, specifically elementals of the related element.
The types are
A stack of 10 of any mote can be made into a Primal (of the same element), i.e. 10 Mote of Water → 1 [Primal Water]. The reverse conversion is not usually possible, but see Earth Shatter and Fire Sunder as exceptions.
Engineers can also use a [Zapthrottle Mote Extractor] to gather motes from gas clouds in Outland.