In RxJS, the `from` and `of` operators are used to create observables from different types of data sources. Although they may seem similar, there is a fundamental difference between them: 1. `from`: The `from` operator is used to create an observable from an array-like, iterable, or promise-based data source. It emits each item of the source one by one. 
  
 import { from } from 'rxjs';

   const arraySource = from([1, 2, 3, 4, 5]);
   // Emits: 1, 2, 3, 4, 5

   const stringSource = from('Hello');
   // Emits: 'H', 'e', 'l', 'l', 'o'

   const promiseSource = from(fetch('https://api.example.com/data'));
   // Emits the resolved value of the promise
The `from` operator is suitable when you have a collection of items, such as an array or iterable, and you want to emit each item sequentially. 2. `of`: The `of` operator is used to create an observable that emits a sequence of values. It emits all the provided values immediately. 

   import { of } from 'rxjs';

   const source = of(1, 2, 3, 4, 5);
   // Emits: 1, 2, 3, 4, 5
The `of` operator is useful when you want to create an observable that emits multiple values immediately, without the need for any asynchronous operations or iteration. Conclusion : In summary, the main difference between `from` and `of` lies in the type of data sources they can handle and the way they emit values. `from` is used for array-like, iterable, or promise-based data sources, emitting values one by one. `of` is used to emit a sequence of values immediately.