Before Steve Jobs returned in the late 90s, Apple's Mac range was a hot mess. Apple was trying to compete with the entire range of PC manufacturers, so in addition to licensed third-party Mac clones, they were making multiple ranges of desktop Mac with overlapping specs, on the principle that they could occupy one shelf slot per machine in Fry's or Target with each model. So you had the Centris, the Performa, and the Quadra ranges, with high, middle, and low end machines in each range, educational and professional media authoring variants, and the powerbook range ...
Jobs returned and priority #1 was to staunch the cash haemorrhage. Rationalizing the product range and supply chain was a huge part of this. So he drew a simple diagram. X-axis: consumer and professional. Y-axis: desktop and portable. Four models would occupy the entire grid, with roughly three specification levels in each (think Goldilocks and the Three Bears). This gave us the iBook and iMac machines (consumer), and the Powerbook and Mac Pro machines (professional), with differentiation based on CPU speed/memory/disk capacity within each cell.
This made the choice of which machine to buy vastly easier on the customer; it was glaringly obvious which model you wanted, all you had to do was decide how much speed/memory/disk capacity you needed, and that was it, rather than trying to figure out what the difference was between a Centris 630 and a Quadra 630AV (hint: RGB video out, 10MHz, and about $250) and so on ...
This turned the precipitous decline in Mac sales around. It took years to build up to the current powerhouse, but it staunched the arterial bleeding -- and all by giving the customers less choice, not more.