Fairy kei is originally a type of Japanese street fashion, which has expanded to inclue more aesthetics-focused aspects.
The clothing focuses on an innocent and playful quality, and frequently uses pastel colors (most often, light/pastel pink). Pastel colors in general are often used, but neon colors are also an option.
Abundance is also often a part of the fashion statement, although not always. Fairy kei wearers love wearing a lot of hairclips and bracelets, even multiple pants on occassion.
Frilly tulle is also appreciated, especially when layered.
Shorts (such as culottes) and miniskirts are the preferred choice for what to wear on your lower half. Fairy kei often features shoes with high soles (i.e. platform mary janes).
The retro anime Creamy Mami is hailed as a large part of the aesthetic by fairy kei lovers.Often, fairy kei and sweet lolita overlap, so a lot of things that are pleasing to lolita wearers are also pleasing to fairy kei lovers.