See Advanced Player's Guide pg. 266
A creature with this trait has the aasimar versatile heritage. Aasimars are planar scions descended from celestial beings. An ability with this trait can be used or selected only by aasimars.
You gain access to these feats.
Aasimar's Mercy, Agathion Magic, Angelic Magic, Angelkin, Archon Magic, Azata Magic, Blessed Blood (Aasimar), Call of Elysium, Celestial Eyes, Celestial Lore, Celestial Resistance, Celestial Strikes, Celestial Wings, Celestial Word, Divine Countermeasures, Emberkin, Empyreal Blessing, Enforced Order, Eternal Wings (Aasimar), Flame Jump, Garuda Magic, Garuda's Squall, Halo, Healer's Halo, Idyllkin, Lawbringer, Musetouched, Peri Magic, Plumekith, Purge Sins, Radiate Glory, Summon Celestial Kin, Tranquil Sanctuary, Truespeech
For example, celestial wings, p36, is as such.
With effort, you can call forth magical wings from your back, similar in appearance to those of your celestial forebears. These wings remain for 10 minutes. You gain a fly Speed equal to your Speed while you've manifested your wings.
Without this trait or some other access, you can't use this feat.