Preload? Shocks

[UncleRico]

Can anyone explain in generic terms what they mean by preload when they speak of shocks and how you compare different shocks with regards to "preload"?

[TRX450R_Racer]

Preload is when you crank down on the spring and "preload" it so there is tension without weight on it. Depending on what brand shock you are talking about, some have zero preload.