Creating a field in Core Data

Creating a field in Core Data

I am new to using Core data. I want to save the picture that the user took
in the app and let the user choose a category for example vegetables,
meat,etc. I was reading a book and came to a sentence that says"create a
field in the Core data entity that will denote the category" I don not get
"create a field in the Core data" Does this mean attributes or something
else?