In Google Analytics, the Average Session Duration is a metric that shows the average length of time users spend on your site during a single session. It is calculated by dividing the total duration of all sessions (in seconds) by the total number of sessions.
To view the Average Session Duration in Google Analytics, go to the "Audience" section and click on the "Overview" submenu. The Average Session Duration will be displayed in the "Session Duration" metric. You can also find this metric in the "Audience" section under the "Behavior" submenu.
Keep in mind that the Average Session Duration reflects the time users spend actively engaged with your site. If a user leaves your site open in their browser and walks away, that time will not be included in the Average Session Duration.