In NVivo, cases are codes that represent the 'units of analysis in your research project. It is not required for all projects to create cases and case classifications. However, if you would like to analyze the variation of opinions for demographic information, such as age and gender, then it is a good idea to create cases and assign attribute values to them.
In this video, I try to explain the rationale behind why researchers decided to create cases and assign attribute values through case classifications. Then, explained how we use this information to perform queries for answering questions like:
How do attitudes vary towards commercial fishing based on participants' community?
Do opinions about economic issues differ based on age and gender?
I hope this helps,