Abstract Class -Real Time Example

Question

In a recent interview, I was asked a broad question on "what is abstract in Java." I gave the concept, and then there were further questions about abstract, such as what is an abstract method and what is the difference between an abstract method and a concrete method, and so on. Finally, the interviewer asked me to offer a real-world example of when I should utilise or define an abstract class. I became perplexed. I provided an example, but he seemed unconvinced.

I looked it up on the internet but couldn't find anything useful.

So, can someone provide me a real-world example of when and why he defined a class as abstract in his project?