OLED vs AMOLED?

According to various news outlets that covered the Droid Ultra/Maxx announcement, all reports seem to indicate that these phones are sporting OLED displays. The Mini, on the other hand, is said to have an AMOLED one. Can anyone shed some light on the differences here, and what would make OLED more desirable over AMOLED?

Edit: Guess they were just using the two interchangeably.