You might of heard someone say Satoshi and wondered what it was. Normally people say the full name of the unknown creator of the bitcoin whitepaper so if you hear Satoshi its most likely a unit of measurement of bitcoin like a penny but as a ratio of 0.00000001 BTC instead of .01 for a penny.
This is how Wiki and google explain if you google what is Satoshi:
"Satoshi Nakamoto is the name used by the presumed pseudonymous person or persons who developed bitcoin, authored the bitcoin white paper, and created and deployed bitcoin's original reference implementation. As part of the implementation, Nakamoto also devised the first blockchain database."