A good explanation of this is on page 125 in "Squeak By Example". Here's the relevant part. For your case its likely that only the first part matters ... just classes in a given class category that you created.
A package named Foo contains:
1. all class definitions of classes in the category Foo, or in categories with
names starting with Foo-, and
2. all method definitions in any class in a protocol named *foo or whose
name starts with *foo- (when performing this name comparison, the
case of the letters in the names is ignored), and
3. all methods in classes in the category Foo, or in a category whose
name starts with Foo-, except for those methods in protocols whose
names start with * .