Lines represent the 500mb height field, which is used to determine location and orientation of troughs and ridges. Additionally, assuming coriolis and friction forces didn't exist winds would flow parallel to height lines, which isn't a horrible assumption 99% of the time.
Colors indicate vorticity, which indicates the tendency for atmospheric rotation. This graphic only depicts positive vorticity (i.e. cyclonic rotation). Pairing cyclonic vorticity with wind yields cyclonic vorticity advection (CVA), which implies warm air advection and upward vertical motion consistent with cyclogensis and/or precipitation development.
More specifically, the height field indicates a deep 500 mb low centered near Chicago with an energetic and negatively tilted shortwave trough rotating north along the east coast with strong cyclonic vorticity advection (image 1) . The surface analysis indicates a powerful surface low (969 mb) centered east of Buffalo, NY where CVA is particularly large (image 2) ... Keep in mind this 11 day forecast was 5 days old at the time of this post and should not be taken seriously, I presented it for learning purposes only.