The Centre for Effective Altruism, a key organization in the EA space, describes effective altruism as both "an intellectual project, using evidence and reason to figure out how to benefit others as much as possible" and "a practical project: to take action based on the research, and build a better world".
MacAskill, William (2019) The definition of effective altruism, in Hilary Greaves & Theron Pummer (eds.) Effective Altruism: Philosophical Issues, Oxford: Oxford University Press, pp. 10–28.
Centre for Effective Altruism (2021) Home, Centre for Effective Altruism.