Mp3, aac, vorbis et al are all lossy compression algorithms. If you rip a CD with any of these, at any bit rate, the result will never be identical to the sound content of the original CD. At high bit rates, most people, especially casual listeners, won't be able to tell the difference. At lower bit rates, you'll be able to discern a difference. Whether the difference in quality is large enough to bother you varies from one person to the next.
Any lossless compression algorithm is just that; the content takes up less space, but when it is uncompressed, it is bit for bit identical to the original source. There is no degradation in quality. The price you pay is space. Most lossless compressors for audio get you around 50% space savings.
From my experience, Apple lossless compression takes up about 3 times as much disk space as AAC at 192 kbps, give or take.
HTH