The BCG matrix is a tool used in strategic management to evaluate the relative performance of a company's business units or products. It plots a company's business units or products on a grid with two axes: market growth rate and market share. The result is a visual representation of which business units or products are "dogs," "cash cows," "question marks," or "stars." This can help a company determine which business units or products to invest in, divest from, or hold steady.