What is the difference between a shift and a movement in the demand (or supply) curve?
A shift in the demand curve occurs when there is a non-price determinant of demand, including a change in consumers' income, changing trends and tastes, changes in the price of complementary and substitute goods, population changes and expected future prices, income and credit. This is illustrated by a shift in the demand curve from D1 to D2 or D3 (as seen in the diagram) depending on whether this determinant increases or decreases demand.
A movement along the demand curve arises from a change in price and it remains in the same demand curve (as seen in the diagram). This also applies to the supply curve, where shifts arise from changes in the price of factors of production, change in the price of a jointly supplied or competitive supply good, changes in technology, productivity, government policies i.e. taxes and subsidies, amongst others.
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