Classes on catalog items are similar to 'task types' on Tasks, or 'Classes' in the CMDB.
Essentially they are all separate tables in the database, but are extended from the same root 'catalog item' table. (just like how incident, problem, change, etc. extends from task).
As a result, when you apply business logic or create a field at the catalog item level, it applies to all child tables (classes). In the same regard, this is why when you look at a catalog item list view, it will include child table table rolled up (e.g. record producers, standard change definitions, etc.)
Granular classes like above lets you edit a form or business logic just for a specific type of record. It also means that the behavior can be unique.
ERM4SN - Table - sc_cat_item «Catalog Item »
