Many of Auto Hand's components come with a "Controller Link" component, which is responsible for converting the controller input of your input package (XR, SteamVR, OVR, and OpenXR) into a function for the module.
This script is responsible for calling the hands Grab, Release, Squeeze, and Unsqueeze functions
Grab axis is a legacy value which will take a trigger axis and set your hands grip accordingly (from 0-1), this system is old and a newer system has taken its place which allows for individual finger control through input
Seen here: Finger Benders โ
Auto Hand includes a "controller event" component for each input system which will take an input value and call a public OnPress/OnRelease Unity Event
For more information on hand tracking see this page