What is the difference between a deterministic and nondeterministic finite automaton?

The next possible state is clearly set in a deterministic finite automaton. A non$-$deterministic finite automaton may have many next possible states.

Deterministic finite automaton can transition to and be in multiple states at once for a given input

Nondeterministic finite automaton can transition to but cannot be in multiple states at once for a given input

They are identical