Buddha - this refers to both the historical figure of Buddha and the Buddha ideal. Taking refuge in this means believing in the Enlightenment achieved by the Buddha, trusting in his teachings, and being motivated to achieve a similar experience. Buddha means perfect wisdom and seeing reality as it is
Dharma - the Buddha's teachings leading to the cessation of suffering
Sangha - a gathering of monks and nuns, upholding the Buddha's teachings and providing examples of their truthfulness - these are all Dharma practitioners