Parallax

Look out of a moving train: the fence next to the track flies past while the mountains barely move. Animators and web designers reproduce that by moving layers at different speeds. In a parallax shot, the foreground might move twice as fast as the midground, and the background very slowly.

Parallax can be faked in pure 2D by moving layers at different rates, or obtained naturally in 2.5D and 3D, where layers sit at real depths and a moving camera creates the effect automatically.

Parallax adds depth and motion to otherwise static visuals, which helps a scene feel alive without adding information. In an explainer, it can guide the eye from a background context to a foreground detail.

Used too much, it becomes noise. Large parallax moves behind text make the text harder to read, and constant movement can be tiring on a phone. It works best as a short accent on a transition or an establishing moment, not under every sentence.

An explainer about cities and heat opens on an illustrated skyline with three layers: buildings in front, a hazy row of towers behind, and the sky with the sun. The camera drifts right; the front buildings slide faster than the towers, the sun barely moves. Then a temperature label pops in over the front layer, which stops moving as the narration reaches the number.