SQL: Structured Query Language - Oracle 10g Database Administration Concepts and Implementation Made Simple - page 48

Figure 2-14: Organizational Chart. Showing chief's Schema. Each user
we create in Oracle is considered as a Schema. Each object created by
user lies under his/her schema. DBA is the owner of all the schemas
and hence all the objects within each of these schemas.
Each user we create in Oracle database is a “Schema”. All the
objects (tables, Views, Sequences etc.) created by that user fall
under his schema. Oracle DBA (Database Administrator) is the
owner of all the schemas and the objects under each. He is just
like the “Chief” in the above figure.
To create table first you have to decide which schema you want
this table to be in. Then log into Oracle system (usually
SQL*Plus) using that schema's (or User's) credentials i.e.
username/password. Upon successful login, execute the
CREATE TABLE command to create required table under that
schema.