You have 3 technologies:-

RPR = Route Processor Redundancy:-

Router Processor Redundancy (RPR) is an alternative mode to HSA and allows Cisco IOS software to be booted on the standby processor prior to switchover (a "cold boot"). In RPR, the standby RP loads a Cisco IOS image at boot time and initializes itself in standby mode; however, although the startup configuration is synchronized to the standby RP, system changes are not. In the event of a fatal error on the active RP, the system switches to the standby processor, which reinitializes itself as the active processor, reads and parses the startup configuration, reloads all of the line cards, and restarts the system.

RPR+ = Route Processor Redundancy Plus:-

In RPR+ mode, the standby RP is fully initialized. The active RP dynamically synchronizes startup and the running configuration changes to standby RP, meaning that the standby RP need not be reloaded and reinitialized (a "hot boot"). Additionally the line cards are not reset in RPR+ mode. This functionality provides a much faster switchover between the processors. Information synchronized to the standby RP includes running configuration information, startup information on the Cisco series Internet routers, and changes to the chassis state such as online insertion and removal (OIR) of hardware. Line card, protocol, and application state information is not synchronized to the standby RP.

SSO = Statefull Switch Over:-

SSO mode provides all the functionality of RPR+ in that Cisco IOS software is fully initialized on the standby RP. In addition, SSO supports synchronization of line card, protocol, and application state information between RPs for supported features and protocols (a "hot standby").

HTH.