A schema export is specified using the SCHEMAS parameter. This is the default export mode. If you have the DATAPUMP_EXP_FULL_DATABASE role, then you can specify a list of schemas, optionally including the schema definitions themselves and also system privilege grants to those schemas. If you do not have the DATAPUMP_EXP_FULL_DATABASE role, then you can export only your own schema.
The SYS schema cannot be used as a source schema for export jobs.
Cross-schema references are not exported unless the referenced schema is also specified in the list of schemas to be exported. For example, a trigger defined on a table within one of the specified schemas, but that resides in a schema not explicitly specified, is not exported. This is also true for external type definitions upon which tables in the specified schemas depend. In such a case, it is expected that the type definitions already exist in the target instance at import time.
"SCHEMAS" for a description of the Export SCHEMAS parameter