Can you buy a digital book?

Could you please elaborate on the concept of purchasing a digital book? Is it possible to acquire a book in a digital format, and if so, how does one go about doing it? Are there specific platforms or websites where digital books can be bought? Are there any advantages or disadvantages to owning a digital book over a traditional, physical book? Is there a process for transferring ownership of a digital book, similar to how one might buy and sell a physical book?