are "high involvement" products for which consumers generally search for information, evaluate different models and compare prices and take time to make a selection
means adding further items in that part of a product range which a line already covers, in order to compete in competitors' niches, to utilize excess production capacity and so on
means lengthening a company's product line either moving up-market or down-market in order to reach new customers, to enter growing or more profitable market segments, to react to competitors' initiatives and so on