In Maya, a directed acyclic graph (DAG), defines elements such as the position, orientation, and scale of geometry. The DAG is composed of two types of DAG nodes, transforms and shapes.
Transform nodes—Maintain transformation information (position, rotation, scale, etc.) as well as parenting information. For example, if you model a hand, you would like to apply a single transformation to rotate the palm and fingers, rather than rotating each individually—in this case the palm and fingers would share a common parent transformation node.
Shape nodes—Reference geometry and do not provide parenting or transformation information.
In the simplest case, the DAG describes how an instance of an object is constructed from a piece of geometry. For example, when you create a sphere, you create both a shape node (the sphere) and a transformation node that allows you to specify the sphere’s position, scale, or rotation. The transformation node’s shape node is its child.
