SCCM 2007 supports the following 14 Site System roles, with those prefixed with being new to SCCM:
Site Server - The server on which you install the SCCM software.
Site Database Server - The server running SQL and hosting the SCCM Site Database (only required for Primary Sites)
Configuration Manager Console - The interface for administering SCCM. Installed by default on Primary Site Servers this role can also be installed on workstations to allow remote administration.
SMS Provider - The intermediate Windows Management Instrumentation (WMI), layer that sits between the Configuration Manager Console and the Site Database (the Configuration Manager Console accesses the Site Database via the SMS Provider). Only required for Primary Sites.
Component Server - All SCCM Site System roles (except for the Distribution Point (DP)), requires SCCM-specific software to be installed in order for the Site System role to function. When such software is installed on a computer that computer becomes a Component Server.
Distribution Point (DP) - Stores SCCM Packages from where Clients can access them to install them. Only required for the Software Distribution, Software Updates, and Advertised Task Sequences functions of SCCM.
[NEW] Fallback Status Point - A "catch all" Site System for Clients that cannot be installed because of various issues such as assignment, or their inability to communicate with their Management Point (MP). Not required by default, but recommended to help with Client installation issues.
Management Point (MP) - SCCM Clients do not communicate directly with the SCCM Site Server and vice versa. Instead all communication is facilitated via the Management Point. A Default Management Point needs to be defined in every Site that has Intranet Clients.
[NEW] Pre-boot Execution Environment (PXE) Service Point - The Site System that responds to any computers requesting deployment of their Operating System (OS), via a PXE request. Only required if Operating System Deployments (OSD), are going to take place using PXE boot requests.
Reporting Point (RP) - Hosts the Report Viewer component that provides the web-based reporting functionality of SCCM. Only required if Reports need to be run on a particular Primary Site.
Server Locator Point (SLP) - Responsible for informing SCCM Clients which MP they should access in order to install the SCCM Client software. Only required in some Client Deployment scenarios.
[NEW] Software Update Point (SUP) - Assigned to the computer running Windows Server Update Services (WSUS). Only required if the Software Updates feature is going to be used.
[NEW] State Migration Point (SMP) - Stores the user's state migration data when a computer's OS is migrated. Only required if the OSD feature is going to be used.
[NEW] System Health Validator Point (SHVP) - This role is assigned to the computer running the Network Policy Service. Only required if the Network Access (NAP) feature is going to be used.