Here is a list of all documented files with brief descriptions:

libimobiledevice
afc.h	Access the filesystem on the device
bt_packet_logger.h	Capture the Bluetooth HCI trace from a device
companion_proxy.h	Companion proxy support
debugserver.h	Communicate with debugserver on the device
diagnostics_relay.h	Request iOS diagnostic information from device
file_relay.h	Retrieve compressed CPIO archives
heartbeat.h	Send "heartbeat" to device to allow service connections over network
house_arrest.h	Access app folders and their contents
installation_proxy.h	Manage applications on a device
libimobiledevice.h	Device/Connection handling and communication
lockdown.h	Manage device preferences, start services, pairing and activation
misagent.h	Manage provisioning profiles
mobile_image_mounter.h	Mount developer/debug disk images on the device
mobileactivation.h	Handle device activation and deactivation
mobilebackup.h	Backup and restore of all device data
mobilebackup2.h	Backup and restore of all device data (mobilebackup2, iOS4+ only)
mobilesync.h	Synchronize data classes with a device and computer
notification_proxy.h	Observe and post notifications
ostrace.h	System log and tracing capabilities
preboard.h	Service to 'preboard' a device, which allows to ask for passcode during firmware updates
property_list_service.h	Definitions for the PropertyList service
restore.h	Initiate restore process or reboot device
reverse_proxy.h	Provide a reverse proxy to allow the device to communicate through, which is used during firmware restore
sbservices.h	Manage SpringBoard icons and retrieve icon images
screenshotr.h	Retrieve a screenshot from device
service.h	Generic basic service implementation to inherit
syslog_relay.h	Capture the syslog output from a device
webinspector.h	WebKit Remote Debugging