Unity's legacy input manager includes a standard Input Manager for accessing traditional game controllers, keyboard, mouse, and mobile touchscreen input. This includes specific button presses and joystick axes. It also supports input from VR and AR input controllers mapped to logical input axes.
The Input Manager provides an abstraction layer over the physical input devices. You can define logical inputs, such as the Fire1 button to fire a gun, which may be mapped to a physical finger trigger button. Unity has a collection of preset inputs that are available when you create a new project. You can review and edit these settings in your project in the Input Manager settings window (Edit|Project Settings|Input Manager). For a general overview and details of the Unity Input Manager, see https://docs.unity3d.com/Manual/ConventionalGameInput.html.
The hand controllers for VR often have a lot of different buttons and axes, and it can...