Oracle SQL Programming - Sequences, Indexes & Synonyms
Sequences are used to serialized fields, although in Oracle 12G the IDENTITY feature can be used (similar to other database systems).
Indexes help us organize physical data in a way to increase efficiency; 3 types of indexes are explained in this video (Bitmap, B-Tree and Table).
Finally, this video discusses synonyms, which allow the aliasing of object names in Oracle.