The ALL_SYNONYMS view provides information on all synonyms that the current user can reference.

ownerTEXTUser name of the synonym owner.
schema_nameTEXTName of the schema in which the synonym resides.
synonym_nameTEXTName of the synonym.
table_ownerTEXTUser name of the object owner.
table_schema_nameTEXTName of the schema in which the table resides.
table_nameTEXTName of the object that the synonym refers to.
db_linkTEXTName of any associated database link.