Forum OpenACS Q&A: Re: Which are the differences between the functions content_type__drop_type and content_type__drop_attribute?
types are somewhat similar to classes in object oriented programming: they are used to define different kinds of things (e.g. persons, parties, content-items, ...).
Attributes are used to describe these different kind things (attributes of persons are first names, last names, email addresses, etc.). If one would have types but no attributes, it would not be possible to store information about these things.
The functions with "drop" are used to delete types/attributes, the ones with "create" .... i am sure, you got it.