Product life cycle describe how a product emerge, grow and at last decline. A corporation plays with variety of products. And every product's life cycle has a direct influence on its portfolio analysis.
The following figure tries to describe the relationship graphically:
Ideally, a company should enter the product/market segment in its introduction stage, gain market share in its growth stage, attain a position of dominance on its maturity stage and maintain this dominant position until the product/market enter in its decline stage, and then determine the optimum point for liquidation.
This also remind about the importance of portfolio analysis, and thus to decide, in which question mark, the corporation should invest. If the question mark fails to create market share, then it directly falls down to dog and a lot of money waste along with valuable time.