CC Madhya 20.368
sākṣāt-śaktye ‘avatāra’, ābhāse ‘vibhūti’ likhi
śakti-āveśa — empowered incarnations; dui-rūpa — two categories; mukhya — primary; gauṇa — secondary; dekhi — I see; sākṣāt-śaktye — when there is direct power; avatāra — they are called incarnations; ābhāse — when there is indication; vibhūti likhi — they are called vibhūti, or possessing special favor.
“Empowered incarnations are of two types — primary and secondary. The primary ones are directly empowered by the Supreme Personality of Godhead and are called incarnations. The secondary ones are indirectly empowered by the Supreme Personality of Godhead and are called vibhūti.