Ridges and Trough aloft - Highs and Lows at the Surface
500 mb Chart
Notice that ridges aloft are associated with Highs at the surface
Troughs aloft are associated with Lows at the surface.
This association of ridges/troughs with Highs/Lows occurs most of the time, BUT NOT ALWAYS
The surface lows are referred to as (midlatitude) cyclones
The surface highs are referred to as anticyclones