Your project needs places not just for its data sources but for the ideas that you bring to it and themes you generate from the data. As you work with your sources, you will gather and explore existing and new categories for thinking about them.
Nodes are containers for these ideas within your NVivo project and contain the evidence within your sources supporting them. Creating and exploring nodes is a way to think 'up' from the data and arrive at higher level explanations and accounts.
Coding is the process by which you nominate a portion of a source which relates to a node.
NVivo provides different types of nodes which are suited to different types of ideas and concepts you are likely to represent in your project:
Free Nodes can be used as containers for 'loose' ideas which are not conceptually related to other nodes in your project. As your project develops, these may be moved into a logical place in your tree nodes.
Tree Nodes can be used to represent the concepts and categories in your project which are logically related as they can be organized in a hierarchical structure (i.e. category, subcategory)
Cases represent the entities within your research (i.e. people, schools, institutions, families). These can also have 'attributes' to record the characteristics of those entities that you want to ask about. Cases, like tree nodes can also be organized hierarchically.
Matrices can be used to show how the contents of different nodes relate to each other. They are created by querying your data using matrix coding queries and are presented in a tabular format.
Relationships represent what you know or discover about relations between items in your project.
You may have determined some of the themes or topics you want to represent as nodes in your project prior to exploring your sources, perhaps as a result of your prior investigation into the literature or the key areas in your interview questions. As you work through your sources, you may find a number of additional themes or topics that you also want to represent as nodes.