A container is a collection of schemas, objects, and related structures in a multitenant container database (CDB). Within a CDB, each container has a unique ID and name.
A CDB includes zero, one, or many customer-created pluggable databases (PDBs) and application containers. A PDB is a portable collection of schemas, schema objects, and nonschema objects that appears to an Oracle Net client as a separate database. An application container is an optional, user created CDB component that stores data and metadata for one or more application back ends. A CDB includes zero or more application containers.