Difference b/w full key and companion key

[biird09]

What is the difference in software functionality when full key is inserted as compared to when companion key is inserted?
I am new with the SW and need to make a presentation, so dont have much to time to play around and figure it out..

Thanks,   

[Jerry]

a full key allows full functionality. A companion key will not allow any acquisition of new data but will allow reprocessing and plotting.