What is the difference between Return true & Return false?

return statements in esql code RETURN;
RETURN TRUE;
RETURN FALSE;
RETURN UNKNOWN;
RETURN ((priceTotal / numItems) > 42);

RETURN TRUE:
1- Propagate message to Out terminal(in case of compute and database nodes).
2- Propagate message to True terminal in case of FILTER node

RETURN FALSE: 
Stop propagation (compute node and database node) & 
Propagate message to False terminal (FILTER NODE) 

RETURN UNKNOWN: 
Propagate message to Unknown terminal OF FILTER NODE.