A graphic visualisation of the 'life cycle' of a product that shows the relationship between sales and time. It can also be drawn to compare time, costs and revenue etc.

The product life cycle is an important concept when developing a marketing strategy, each stage should suggest the emphasis of marketing effort.
Raise awareness through advertising
Sell into supply chain
Target early adopters
Product might only offer basic features
Still need to generate high levels of awareness - possible develop Brand
Ensure high levels of coverage in supply chain - build relationships to create barriers
Consider reduced price to grow share
Develop product range to offer more features
Prior to maturity there might be a period of shake-out Do you stop in the market or move to another?
Protect market share
Rationalise product range
Harvest profits
Remaining customer base migth be less price sensitive
Rationalise distribution
See also Boston Boxes/BCG Matrix
There are also strategies to extend the life cycle

The product life cycle is linked to other life cycles - the market life cycle; the technology life cycle and the industry life cycle.