What is different about amazon sessions vs impressions

Just wondering what is difference between amazon sessions vs impressions?

I see two differ reports from PPC (amazon sponsored products) and business one. I found out impressions is always high then sessions? Any idea about what is different between sessions and impressions?

Any helping will be appreciate.

If you go to the Amazon site and browse around, you will register a session – 1 session. When you visit any random product page, you will tally 1 session and 1 impression (page view) for that product page. If you go back to that product page again – lets say 10 minutes later, you will tally another impression but not another session.

So, if your product page had 100 sessions yesterday and 200 impressions, that means each session (visitor) averaged 2 visits to the product page.

In other words, sessions would be the count of unique viewers of the product while impressions would be the total view count from those unique viewers.

I believe that Sponsored Products sessions last up to a week, unless the visitor clears his cache and cookies.