Final answer:
In Android development, an XML file with an animator resource type that utilizes an animation list is for creating frame-by-frame animations, with each item tag representing a single frame.
Step-by-step explanation:
When an XML file of the animator resource type is added to an Android project, the animation list is indeed used as the root XML element if you are creating a frame-by-frame animation. This animation list contains a series of <item> tags, each one pointing to a drawable resource that represents a frame of the animation. These frames are displayed in sequence to create the animation effect. It's important to remember that the items within the animation list should be ordered the way you want the animation to progress, and properties such as the duration for each frame are also specified within the item tags.