What are troughs and ridges I always hear meteorologists talking about?

TroughThese are patterns in the upper atmosphere that are directly related to the weather near them. The upper atmosphere is dominated by several jet streams which are distinct rivers of air, and these are prone to bend and close off, simliar to the way a river of water flows around rocks. Troughs are associated with rising air and storms, and are curved counter-clockwise or cyclonically in the northern hemisphere. Ridges are associated with descending air and nice weather, and are curved clockwise or anti-cycloncally in the northern hemisphere.