Client agents are SCCM 2007 components that run on top of the base client components.
Computer Client Agent Properties-Configures how often client computers retrieve the policy that gives them the rest of their configuration settings.
Device Client Agent Properties-Configures all of the properties specific to mobile device clients. Hardware Inventory Client Agent-Enables and configures the agent that collects a wide variety of information about the client computer.
Software Inventory Client Agent-Enables and configures which files Configuration Manager inventories and collects.
Advertised Programs Client Agent-Enables and configures the software distribution feature.
Desired Configuration Management Client Agent-Enables the client agent that evaluates whether computers are in compliance with configuration baselines that are assigned to them.
Remote Tools Client Agent-Enables Configuration Manager remote control
Network Access Protection Client Agent-Enables Configuration Manager Network Access Protection
Software Updates Client Agent-Enables the agent that scans for and installs software updates on client computers.