Jetstreams are fast moving wind belts up to 9km above the surface. They are located at the “top” of the atmosphere spiraling from west to east around our mid-latitudes at speeds around 200mph. They are important in controlling weather at the surface.
Our own jetstream (the “polar-front jetstream”) usually marks the boundary between tropical air and polar air. This week the jetstream is mostly to the south of the UK and is dragging some big depressions (low pressure areas = storms) across the Atlantic bringing wet and windy weather to Reigate by Wednesday / Thursday.
You can think of jetstreams dragging depressions (storms) along on a tight lead like owners of badly behaved dogs trying to restrain their hounds in the local park. Heel boy!