i have read a few posts about safe mode but what is this?

there was 1 i read and he was saying he was on his way home from a remap and this happened i got the impression that the car only ends up doing 50 ish mph why? and how do you get it back to normal?

 

its a setting on the ecu that comes into play if it detects a problem which enables you to get the car home safely, i think im right by saying it can only be corrected by pluging the ecu into a computer and finding out what the problem is,then resetting the ecu