https://download.schneider-electric.com/files?p_Doc_Ref=EIO0000001578&p_enDocType=User+guide
The context corresponds to the last state of the customer application, for example if the CPU was sending a communication to a device during the power outrage, it will save the state and allow the warm start. It will restart from the beginning of the communication to continue the application process where it has stopped before the outrage. The context is supposed to be saved without being lost, the only way to change the context is to power down the system. This will also depend on the health of the memory.
If the context is valid this will allow the CPU warm start. Otherwise, this will result in a cold start from which the CPU is completely restarts the application from the beginning.
