Hey there,
Google is your friend, my friend. WAV, AIFF, FLAC, and ALAC are all lossless.
WAV and AIFF are very similar. They are both containers for RAW PCM audio. WAV was originally a Microsoft/IBM standard and AIFF was originally an Apple standard. They both preserve the PCM audio from CDs perfectly.
FLAC and ALAC are also very similar, with ALAC being Apple's lossless format. As lossless codecs, they preserve the PCM perfectly just as WAV and AIFF do, but they also use compression algorithms that preserve fidelity and cut the file sizes down by 40%~50% depending on the compression levels.
Be careful when asking the question, "What is best?" The answer is often subjective, but occasionally objective.
A typical audio CD from a store contains two-channel 16-bit Linear PCM audio sampled at 44,100 Hz. This means each file on a typical audio CD sampled the digital information of the source 44,100 times each second and it did so using 16 bits of information. There are some CDs and places online that offer higher sampling rates (96 KHz and 192 KHz among others) and 24-bit audio, which is technically and objectively "better" because it's truer to the source (assuming source sample rate is higher than 44.1 KHz and has a higher bit-depth than 16), but subjectively many people cannot tell a difference.
The general public often struggles to tell the difference between 128 kbps MP3 lossy and WAV lossless so I assure you that the subjective audible difference between 192 KHz 24-bit lossless audio files and 44.1 KHz 16-bit lossless audio files will be beyond miniscule. Some people claim to be able to hear differences like that and I applaud them, but like I said, a lot of people struggle hearing a difference between lossy and lossless. The great part is there are many blind testing tools out there that allow you to try it for yourself and see if you can hear differences. If that's not your cup of tea, a friend can always help out.
128 kbps MP3 files are often "good enough" for most people. That fact in addition to the file sizes achievable with lossy files is why MP3 and MP3 players exploded in popularity. Music sounded "good" and people could carry hundreds of thousands of songs in their pockets.
For those people who do not think 128 kbps MP3 is "good enough" often they will use FLAC, ALAC, or higher bit rate MP3 files (320 kbps). WAV and AIFF are also options, but since FLAC and ALAC preserve the fidelity so well and cut down on the file sizes, there's really no need to use them. I personally use mostly FLAC with a little bit of my collection in 320 kbps MP3, but that doesn't mean I'm right. I just happen to have high end gear that can pick out the differences between high quality and low quality audio files and I have the storage space for the larger file sizes so I don't need the extra compression.
I haven't done any blind tests in a while, but I did do some using some mid-fi gear a while back. I could usually tell the difference between 128 kbps MP3 and FLAC, but the difference between 128 kbps MP3 and 320 kbps MP3 was very difficult to pick out and 320 kbps MP3 and FLAC even more so.
The best thing to do is to try out the various formats and pick what's best for your system and your budget. There are plenty of other options than what I just mentioned as well so don't think that's it. I didn't even speak of vinyl, but I recommend looking into that as well.
I hope that helps and if anything I said was wrong, I ask that someone please correct me. I'm not a professional and I don't claim to be one. I'm just an IT guy who loves music and knows a few things about audio.
Best Regards,
Dan
