Extending north and south from the equator to roughly 23.5° latitude is a region called the tropics. This area is not defined by latitude but by the point at which the sun appears to be directly overhead at its highest point in the day, which is affected by the planet’s axial tilt. Since our imaginary planet can have a different axis than Earth’s, and therefore a different tropical zone, we can invent the area that is our tropical zone. Most of us will want to assume 23.5°, never mention this, and be done.
On Earth, the northern tropic is called the Tropic of Cancer while the southern is the Tropic of Capricorn. We’ll want different names for ours. To make life easier on readers, it might be best to name a tropic after a prominent city located at 23.5°, though doing so requires having drawn latitude lines on a map. Or we can wing it. Stating that a map is not drawn to scale gives us some leeway to be inaccurate. Even on Earth, most people have no idea which tropic is which, where they end, or why they should care. Our readers won’t remember either unless we name the tropics by something they’re more likely to remember, like a prominent city or a kingdom in that tropical zone. The latter frees us from an exact location.
The tropics move heat from the equator toward the poles and are the primary influencer of climates on every continent. Ocean temperatures and mountain ranges further modify climate. A high-altitude area in a tropic zone might have a climate more like a temperate zone.
The subtropics are the next farthest region from the equator, from 23.5° to 40°. On Earth, many deserts are in this zone, which seldom sees a hard frost or snow, but tropical storms and hurricanes can deliver as much as half of a country’s rainfall.
In between the polar and subtropical zones, from 40° to 66° is the temperate zone, where most life on Earth exists. Coastal regions experience milder winters and summers than areas far inland, which experience a greater range in temperatures. Similarly, high altitude areas in this zone might have a climate more like a polar zone. The areas closest to the poles can be considered sub-temperate.
The polar zones cover the north and south poles to 66° latitude and are largely covered in polar ice caps. There isn’t much we need to worry about that isn’t obvious. It’s only mentioned to contrast it with the other zones.