Each element on the canvas has its own layer, which can be controlled from the Layers panel.
You can hide a layer by tapping on the eye icon to the left of the layer name. Hiding layers can be useful to access and modify layers behind the current layer. Layers that are hidden will not be exported when you share an image.
You can reorder layers so that the target layer appears above or below other layers. To reorder layers, simply tap and drag a layer's name up or down in the Layers panel.