Probably a more important distinction between Subject and Observable is that a Subject has state, it keeps a list of observers. On the other hand, an Observable is really just a function that sets up observation.
“When you train your creativity, you automatically train your memory. When you train your memory, you automatically train your creative thinking skills!” — Tony Buzan
“When you change the way you look at things, the things you look at change.” — Dr. Wayne Dyer