What a scene is and how it is different from a chapter?

A scene is just a part of a chapter and a chapter is a long telling of a story or something you are reading.

A scene can mean two things. A scene can be the setting of a story, or (what I think you are referring to) it can be a segment of an Act of a play. A scene separation within a play is usually included in order to allow time for a change in setting during the performance. A chapter is a segment of a book. So, to summarize, a scene is a segment of a play and a chapter is a segment of a book.