Can anyone give me a non-technical description of Core Data and how it is used?

Nehemiah, persistent data just means that the data is persisted, i.e. it continues to exist after the app is closed. So, in Jason's example, once the to-do app was closed, the to-do data would still be stored in core data. And, once the application was re-opened, it would then read the to-do data (from core data) back into the app.

I would say that you're in the ball park when you mentioned entities and data sets. Much like a relational database, core data stores entities (tables), and each of these entities has attributes (fields/columns). Relationships can then be created that connect one entity to another by certain attributes (think foreign key to primary key relationships).

It is a locally based database that allows for your apps to have persistent data while they are installed. A to-do app is a good example of where Core Data can be used.