the sound.... example: A sax and trombone can play the same note but obviously they sound entirely different.
It also applies to specific instruments.... an acoustic guitar and Steves electric can play the same note but the 'tone' will be entirely different.
Now it's obviously more complex than that but that's basically it. Some tones have more appeal to genre or individual listeners. Leslie's 'tone' would work in a Bach Overture... and what works in Back Overture wouldn't work on one of Leslie's songs.
By the way... I agree... his guitar sounds fantastic. - JamesJM