Every type of content in eZ Publish has its own content class, but we have to clearly understand that a content class doesn't store any type of data; it represents a definition of a data structure.
For example, if our site shows some stories on the home page, these stories should be defined by an Article content class that is built on one or more attributes, such as Title, Body, and Publication date.
These attributes are called Class Attributes. As we can see in the following image from the eZ Publish documentation, these attributes are represented by a specific datatype (which is the smallest entity of storage) and describe how a specific content has to be retrieved, validated, and saved:
The class attributes ...