All digital is lossy compared to analog, because you are digitally representing the smooth round analog sound waves with jagged edged graphs, like staircase steps. Higher bit depths (esp.) and sampling rates make the stair steps smaller, so more detail is captured, but it is still lossy.

When you're talking about "lossless digital" you are talking about the compression. mp3 and other lossy codecs throw out data that can't be recovered when they compress, FLAC and SHN do not because they are lossless codecs. All the info deleted when a .wav is compressed to FLAC is redundant data, meaning data that is carried in the other channel of a stereo recording, or elsewhere in the recording. A .wav file is just uncompressed digital audio.