Dwell Time -
It means Actual time spent on a webpage before returning to SERPs page.
(For ex- user search for article then he clicks on first ad then he read and stay for 10min. And he return to back search page (SERPs).
The time he spent on that page that is Dwell Time. 10min of Dwell time.

Bounce Rate -
There are two type of bounce Time

1. Standard Bounce Time -
If user clicks on ad and he go to landing page and finds irrelevant content/high page load time/ then, if he go back with in 6sec i.e Standard Bounce rate.

2. Actual Bounce Time - if user search a query, clicks on ad then he stay on page but he did not clicks anywhere in the page and go back to SERPs that is the actual bounce rate.

On Page Time -
The time spent on a webpage before going to another webpage within the website.