The board support package modules provide abstractions of, and functionality using the Nordic Semiconductor Development Kits.
See BSP indication states for an explanation of the BSP states that are used in some of the examples.
See BSP BLE Button Assignments for documentation of standard BLE button functionality in the SDK examples.
See BSP BLE Button Module for documentation of the BLE button module, and BSP ANT Button Module for documentation of the ANT button module.
See also Board Support Package, BSP: BLE Button Module, BSP: ANT Button Module, and NFC BSP Module for API reference.