Check the visit documentation.
How this metric is calculated
A visit always ties to a time period, so you know whether to count a new visit if the same person returns to your site. A visit starts when the user first arrives on your site. A visit ends when they meet any of the following criteria:
- 30 minutes of inactivity: Almost all sessions end in this manner. If more than 30 minutes lapse between hits, a new visit begins.
- 12 hours of activity: If a user consistently fires image requests without any 30-minute gaps for more than 12 hours, a new visit automatically starts.
- 2500 hits: If a user generates a large number of hits without starting a new session, a new visit is counted after 2500 image requests.
- 100 hits in 100 seconds: If a visit consists of more than 100 hits that occur in fewer than 100 seconds, the visit automatically ends. This behavior typically indicates bot activity, and this limitation is enforced to help increase report performance.
A visit does not necessarily coincide with a browser session because of the above criteria. One of the most common differences is where a visitor navigates to your site, leaves the tab open for more than 30 minutes, then resumes browsing. While this action is technically part of the same browsing session, Adobe considers this action two separate visits.
In general a visit will be counted for both web and mobile SDK implementation. It will always start on first servercall/hit sent to adobe analytics for a specific unique visitor ID and be closed when one of the condition above is met.
The Mobile sessions are different as you will configure in your mobile SDK how long you would like your session to last and the launches metric is more appropriate. Check the mobile metrics documentation. And this one as well.
Some other post that treats the same:
https://experienceleaguecommunities.adobe.com/t5/adobe-analytics-questions/adobe-analytics-for-mobile-apps-visits-session-time-spent-per/m-p/303734
This video should help you as well:
https://experienceleaguecommunities.adobe.com/t5/adobe-analytics-questions/adobe-analytics-for-mobile-apps-visits-session-time-spent-per/m-p/303734