For many of us, CD ripping starts and ends with what you might call the default options; iTunes if we use OSX, XP or Vista and an iPod, or Windows Media Player if we use XP or Vista and just about any other device. If all you want to do is rip AAC or MP3 files from CD for use on your favourite MP3 player or PMP, there's nothing wrong with that - you will get decent results at a decent speed, and you'll be able to drag the finished files over to your player with the minimum of fuss.
However, there are good reasons why you might want to consider an alternative, the biggest being that you want to create a master archive of your CDs in a lossless format. As you probably already know - or can work out by yourself - the vital thing about a lossless format is that no audio information is thrown away. The audio codec isn't doing any jiggery-pokery to cut down file sizes by removing audio data it thinks you can't hear; it's just compressing the whole shebang in the most efficient way it knows how.
Now, both iTunes and Windows Media Player have their own lossless formats (Apple Lossless and WMA Lossless), but they're not necessarily the most efficient formats. Nor are they the formats that will be supported by the majority of playback devices in the future. Opinions differ on the best lossless format, with some preferring the Monkey's Audio format (APE) and some liking True Audio (TTA). However, at the moment the momentum seems to be behind the free, open-source codec, FLAC. It's being used by numerous artists, from Paul McCartney to Pearl Jam to Nine Inch Nails, as a means of distributing high-quality digital music directly to fans, and it's also proving popular with online stores and record companies, including classical heavyweights Deutsche Grammaphon. FLAC is also supported by a growing number of high-end MP3 players and PMPs.
You'll note that we're talking about FLAC as an archive format, rather than a playback format. The fact is that, unless you're listening to an MP3 player in ideal conditions using high-quality headphones or Hi-Fi equipment, you'll struggle to hear any difference between a well-encoded MP3, AAC, OGG or other lossy file and a lossless FLAC or APE file. Serious audiophiles believe that lossy compression results in a loss of tonal depth (due to the removal of borderline-audible frequencies), a smearing of attack (due to the effects of compression and recompression) and the removal of some dynamics, but it's unlikely that you'll recognise these issues on an iPod with a £60 pair of earbuds on a noisy train. Leave your FLAC files at home where they belong, with an environment and equipment that allows you to hear them at their best.
No, the point about archiving to FLAC rather than MP3 is that you create - and can then backup and maintain - a perfect copy of your original CD collection that you can then convert to other formats as and when you need to, either for portable use or for other devices and other formats should they appear. It's a lot faster than ripping from CD again and again and again. As a bonus, you also have the best version sitting on your PC should you want to sit and listen using high-quality speakers or headphones.