System Tables - Oracle

System TableDescriptionColumns
ALL_TABLES Tables TABLE_NAME, OWNER, NUM_ROWS
ALL_TAB_COLUMNSTable Columns OWNER, TABLE_NAME, COLUMN_NAME, DATA_TYPE, DATA_LENGTH, NULLABLE
ALL_INDEXESIndexes OWNER, INDEX_NAME, INDEX_TYPE, TABLE_OWNER, TABLE_NAME, UNIQUENESS
ALL_IND_COLUMNSIndex Columns INDEX_OWNER, INDEX_NAME, TABLE_OWNER, TABLE_NAME, COLUMN_NAME, COLUMN_POSITION, COLUMN_LENGTH, DESCEND
ALL_OBJECTSObjects OBJECT_NAME, OBJECT_TYPE

Valid Object Types: INDEX, SEQUENCE, TABLE, VIEW, etc.