Sessions:
The amount of times a visitor has been on your website.
For example, if a visitor had been on your website on the 5th August and then later returned on the 9th August, it would count as two sessions.
Users:
The amount of unique visitors that have been on your website.
For example, if a visitor had been on your website on the 5th August and then later returned on the 9th August, it would count as one user.
Pageviews:
The total amount of views on all your pages/unique page.
Pages / Session:
The amount of pages that a visitor has visited during their visit to your website.
Avg. Session Duration:
The average amount of time that a visitor has spent on the page of your website.
Bounce Rate:
Bounce Rate is the percentage of single-page sessions (i.e. sessions in which the person left your site from the entrance page without interacting with the page).
The lower the bounce rate percentage, the better. This means more people are exploring your website. However, you do have to bare in mind that users might leave the site after viewing a single page if they’ve found the information they need on that one page, and had no need or interest in going to other pages.
A good bounce rate is around 40-45%.