What is Dora?
Dora are bonus tiles shown by indicators on the table. Each matching tile in your winning hand adds one han (dora does not count as yaku by itself).
Simple hand with dora potential
Tanyao (All Simples)
234 Man
234 Pin
345 Sou
678 Sou
Pair
Ura dora
After a riichi win, hidden ura dora indicators may add more han. See What is riichi? and Glossary: dora.