Preya means immediately palatable, and sreya means ultimately beneficial. That is called sreya. Just like for a child, playing is priya, preya. He likes to play. But he is by force, by the parents, he is studied books. That is called preya. But because without education his future life will be dark, so parents know it. Therefore, although the child likes to play — that is preya — the parents engages them into sreya, into education. So that is the Vaisnava's duty.

These rascals and fools, they are busy in material sense gratification, and it has become the duty of the devotee. Because the devotees mean the servant of the supreme father, Krsna. So they have been engaged. Just like Caitanya Mahaprabhu said, yare dekha, tare kaha 'krsna'-upadesa [Cc. Madhya 7.128]. So devotees are so confidential servant of the Supreme Lord; therefore they are engaged in preaching Krsna consciousness. They have no business for themself — they are completely perfect as soon as they have accepted Krsna — but they are working on behalf of Krsna to turn these two-legged animals to become Krsna conscious.

This is the meaning of Krsna consciousness movement.

Srila Prabhupada, Srimad-Bhagavatam 3.26.29 — January 6, 1975, Bombay