The proper spring rate will allow for the appropriate amount of sag. Sag is the amount the suspension compresses when supporting the rider, riding gear, and a portion of the bicycle. It is measured as a percentage, with the ideal percentage range being between 10-30% of the total available travel (less for shorter travel, more for longer travel). Setting up the suspension to achieve this will allow for maximum traction and an ideal suspension feel.
Lock (L) mode prevents the suspension from compressing. Use Lock mode for maximum pedaling efficiency on smoother terrain.