NVivo offers ample documentation for the different ways to 'code' data.
Coding:
In NVivo, coding data refers to the act of assigning conceptual themes to various sections of textual, image, and video files imported into the application. This is usually accomplished by highlighting the specific data to be coded performing a drag-and-drop maneuver or right-clicking and assigning a Node the the data.
Nodes:
Nodes are a collection of the coded references pertaining to a particular theme. You may think of a node as a container much like a simple file folder that can be used to quickly access and analyze all the materials on a particular subject or aspect of your project.
Below you can find detailed documentation on coding concepts provided by the NVivo developers.
Coding in NVivo
Nodes in NVivo