Dell and Apple are phasing out PCMCIA card slots (sometimes called PC cards, or cardbus cards) in favour a new format that is not backwards-compatible. Whilst most modern laptops feature the sort of things that you once needed to buy cards for (eg: modems, firewire interfaces, etc). there are quite a few people continuing to use specialised cards (eg: 3G/GPRS wireless modems) that will not work in new laptops.