1 Drive in the right lane and pass on the left. 2  If there are three lanes, use the right lane for lower speed driving, the left for passing. 3  If you stay in the right lane, watch for cars entering the expressway.
A scrub is a now generalized term used as a synonym for a noob or newb, which is someone who is bad at a video game or activity in general. Most of the definitions here, surprisingly, have nothing to do with the actual term.
Shrub is a very common word used to describe bushes that people might plant in their yards. Scrub, as a noun, is rather unusual, describing, as Feebs says, certain stunted varieties of trees -- I think I may have heard of scrub oak, but I would have thought scrub was an advective in that sense anyway.