The quantity demanded of a good is influenced by factors affecting consumer's willingness and ability to buy. These include the good's own price, prices of related goods (substitutes and complements), consumer income, tastes and preferences, and expectations. - Good's own price causes a movement along the demand curve. - Price of a complementary good and Price of a substitute good shift the demand curve. - Prices of inputs into production (like labour, raw materials) affect the cost of production. This influences the supply side, shifting the supply curve. It does not directly affect the quantity demanded by consumers at any given price.