Products move through recognizable stages from introduction to decline. The product life cycle describes those stages: introduction, growth, maturity, and decline. In the introduction stage sales are low and costs are high. Growth brings rising sales and profits. Maturity sees sales peak and competition intensify. Decline brings falling sales as customers move to newer alternatives.

Marketing strategies change with the stage. Introduction emphasizes awareness and trial. Growth focuses on share and distribution. Maturity requires differentiation and cost control. Decline may involve harvesting, repositioning, or discontinuation. Not every product follows the classic curve; some are revived, some fail early, and some become enduring staples.

Understanding where a product sits in its life cycle helps managers allocate resources and set realistic expectations. It also reminds organizations that continuous innovation is necessary because even successful products eventually face saturation or substitution. The life-cycle concept remains a practical framework for planning over time.