Prodcut life cycle

The product life cycle goes through many phases, involves many professional disciplines, and requires many skills, tools and processes. Product life cycle (PLC) has to do with the life of a product in the market with respect to business/commercial costs and sales measures; whereas product lifecycle management (PLM) has more to do with managing descriptions and properties of a product through its development and useful life, mainly from a business/engineering point of view. To say that a product has a life cycle is to assert four things: 1) that products have a limited life, 2) product sales pass through distinct stages, each posing different challenges, opportunities, and problems to the seller, 3) profits rise and fall at different stages of product life cycle, and 4) products require different marketing, financial, manufacturing, purchasing, and human resource strategies in each life cycle stage.
The different stages in a product life cycle are:

Market introduction stage
cost high
sales volume low
no/little competition - competitive manufacturers watch for acceptance/segment growth losses
demand has to be created
customers have to be prompted to try the product

Growth stage
costs reduced due to economies of scale and
sales volume increases significantly
profitability
public awareness
competition begins to increase with a few new players in establishing market
prices to maximize market share

Mature stage
Costs are very low as you are well established in market & no need for publicity.
sales volume peaks
increase in competitive offerings
prices tend to drop due to the proliferation of competing products
brand differentiation, feature diversification, as each player seeks to differentiate from competition with "how much product" is offered
Industrial profits go down

Saturation and decline stage
costs become counter-optimal
sales volume decline or stabilize
prices, profitability diminish
profit becomes more a challenge of production/distribution efficiency than increased sales