You are a big fellow compared to others. For every step on this trait you are half a foot taller than average of those of your kin. A character who has Small cannot take this trait without first getting rid of the negative trait.
At +3 and above, your Reach in melee increases by one full step. So Long becomes Very Long, Normal becomes Long etc. This does not make Grappling count as Close, however. Grappling rules still apply.