Specific types of trusts in Active Directory include:
One-way trusts allow users of one domain access to resources in another domain (but not the other way around). Two-way trusts allows users in two domains to access resources in the other domain.
In transitive trusts, if domain A trusts domain B, and domain B trusts domain C, then A will trust C. Intransitive trusts lack this property: A trusting B implies nothing about A's relationship to C.