Music uploaded to RED comes from two main sources: analog media and digital media.
An analog music source must use an analog to digital converter like a sound card to convert physical changes in an analog medium to a digital file that a computer can read. An analog medium is an object that stores music by being physically altered.
Analog recordings can be ripped into digital music files, such as FLAC and MP3. Vinyl records are always approved for uploads, but cassettes are only allowed under strict conditions.
A digital music source has already been encoded into a format that a computer can read, so no conversion is necessary. A digital medium is an object that stores music in digital files (a string of binary numbers).
Please do not mistake WEB downloads for a non-allowed web rip. Web rips mean a lossy (bad) transcode of an audio stream, such as YouTube, or other streaming services.
Digital music sources can be uploaded to RED after using spectral analysis to check for lossy transcodes.
There is still much debate about whether analog and digital sources sound different. Some people prefer the "feel" of vinyl and think that music on vinyl records sounds "warmer" and "fuller". Others think that digital sources provide an unadulterated and pristine listening experience. RED allows both, so you can download and make your own judgment!