Some of the major difference in a tabular form:
|Emits only a single value at a time||Emits multiple values over a period of time(stream of values ranging from 0 to multiple)|
|Eager in nature; they are going to be called immediately||Lazy in nature; they require subscription to be invoked|
|Promise is always asynchronous even though it resolved immediately||Observable can be either synchronous or asynchronous|
|Doesn’t provide any operators||Provides operators such as map, forEach, filter, reduce, retry, and retryWhen etc|
|Cannot be canceled||Canceled by using unsubscribe() method|
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