By shredder, I mean guitarists who play in a style similar to players like Yngwie Malmsteen, Paul Gilbert, Rusty Cooley, Joe Satriani, Michael Angelo Batio, etc.

They play fast and with many notes. They use techniques like
Alternate picking
Legato
String skipping
Sweep picking (often arpeggios)
Tapping
and they usually use their techniques in "flashy" ways.

Their tone is usually heavily distorted, with delay and other effects added in order to make their tone sound smooth and to make it easier to play fast.