Motion Array Graphics Templates are layered. Even if you choose an illustration with a single layer, all of our graphics will contain some level of layers - as a general rule of thumb, the more elements included in the graphic, the more layers may be included.
The Item Details on the product page of a Graphic tell you information such as how many layouts and placeholders are included - these are all layers.
It's great to have layers in case you need to change around the order or appearance of certain layers, for example, adding a character in between a background layer and a foreground layer, or changing the gradient, color or text of a graphic:
Please note that illustrations are pre-created art that may not contain multiple layers, although they include at least 1 layer. Other layers may include Hue/Saturation layers, etc.