Dolly & Zoom shots are often used to visualise your story better.
To understand how dolly and zoom shots work, the attached video can be referred.
As explained in the video, dolly shots are the shots operated from a dolly. You can go towards to your subject and establish it’s importance by doing it. Furthermore, you can track and follow your subject from the side. You also can do a circular track on its requirement in your storytelling.
Zoom shots are the shots where the subject is magnified without moving the camera. You can do a quick zoom or a smoother zoom which often used to convey the mood of storytelling.
Dolly shots sometimes can be considered as the point of view of audiences watching the film depending on how the shot is constructed. Whereas, zoom shots convey the zoning out of the audiences when you are focusing on the subject entirely.
You can also put dolly and zoom together for great effect. Many filmmakers have used them to convey their emotions as it states.
There are no rules for the purpose of using both the kind of shots as it depends on how you want the audience to experience it. There are various ways to utilise dolly and zoom shots which are well explained in the video.
So hopefully now you understand the importance of dolly and zoom better. Play around and don’t hesitate to experiment.