What's The Difference Between a "2 Track" and "Tracked-Out" Beat?

A "2-track beat" aka a "Stereo Beat" is one stereo file. 

• This usually in the format of one MP3 or WAV file 

A "tracked-out" beat means the instruments of the beat (kick drum, snare, bass, synth, etc) are on separate tracks, also known as "stems." 

• This will usually come in a zip folder with multiple WAV files