Lossless audio is the most accurate representation of the recording process' audio. This means that no information has been lost. When audio is converted to a lossy format (such as MP3, AAC, or WMA) quite some information is compressed to reduce the size of the file. Because of this, some audio quality is lost in order to occupy as little space as possible.
When audio is converted to a lossless format (such as FLAC, WAV files, or AIFF), no information is thrown out. Data is only compressed as much as possible but all audio information will always be available. For archiving purposes, one should always use a lossless audio format.
With a Primephonic Platinum subscription, you can stream lossless classical music up to 24bit/192kHz.