There are two kinds of Instancing in TouchDesigner:
1. A geometry instance in the Geometry Component is a copy of a geometry object which can be transformed independently. The Geometry COMP has an Instance parameter page to create instances. Transformations of the instances can be made by supplying CHOP channels with x, y, and z and other data.
2. An instance is an OP that doesn't actually have its own data, but rather just points to (or has an input) whose data it uses. Examples include Null OPs, Select OPs, Switch OPs.