A few hundred km below the cloudtops, hydrogen starts behaving like a liquid. At the center there is a 30 Earth mass core. On a non-rotating planet, the equator heats up, warm air rises, and migrates to the poles where it cools off and sinks back to ground level. When a planet rotates, the equator is moving faster than the poles. Wind moving towards the poles is going too fast, so it turns eastward.
Wind moving away from the poles is going too slowly, so it turns westward.
This causes the circulation to break up into sections called Hadley cells. Where there is upwelling, there is westward motion. Where there's downwelling, there's eastward motion. On the Earth this leads to tropical rainforests, subtropical deserts, temperate rainforests, and dry polar regions. There is a layer of water ice clouds below this.