The Axsy Field Service App sits directly on top of Salesforce. Please see this article for an illustration: Utilising Standard Salesforce FSL Objects
During your use of the Axsy Field Service Mobile App, you are connecting directly with Salesforce over a secure connection and no Axsy servers or systems are needed to enable you to use the mobile app or to process any of your data.
To illustrate the typical use of the Field Service Mobile App you would use it as follows:
When you login, you input your Salesforce username and password and these details are sent directly to Salesforce who authenticate you.
As the Axsy Field Service App is designed to work in an offline mode, the mobile app will synchronise your Salesforce data into the app to enable you to work offline.
When you use the mobile app offline your data is stored locally in the mobile app in an encrypted database. Once you go back online, your data is synchronised from the mobile app back to Salesforce.