Your mobile users' productivity doesn't have to stop when there's no connectivity. When you enable caching and Offline Edit, users can keep working, unimpeded by a subway commute, FAA regulations, capricious cellular signals, or bunker-style buildings. Offline access is available for Salesforce for Android and iOS.
Manage caching and Offline Edit from Setup—enter Offline in the Quick Find box, then select Salesforce Offline.
Work Offline with the Salesforce Mobile App - https://help.salesforce.com/articleView?id=sf.salesforce_app_offline.htm&type=5