What is raga and who are raga worshippers?

Those people who naturally gain satisfaction in worshipping the Lord, without motives of fear, desire or duty, begin their worship with attraction (raga). Raga is defined as the tendency of the mind to become spontaneously attracted to an object immediately on seeing it, without intellectual processing. A person who has developed this quality of attraction in his heart as soon as he thinks of the Lord is worshipping the Lord according to raga. Those who take to worship of the Lord from fear, desire or duty are not on such a pure level . Those who worship the Lord according to raga are real worshippers.

Bhaktivinoda Thakura, Chaitanya Shikshamrita