What are Observables? How they are different from promises?

'Observables', 'Observables', 'Observables'...Yes! Today, we will discuss about the 'fancy' & discussed word of the market, which is 'Observables' and also how they different from Promises (Not heard about Promises? No worry! You will know it soon). Let's start! The term 'Observable', I encountered when I started learning Angular.