Nondeterministic Finite state automaton

Nondeterminism is a useful concept that has great impact on the theory of computation. When the machine is in a given state and reads the next input symbol, we know what the next state will be -it is determined this called deterministic computation but in a nondeterministic machine, several choices may exit for the next state at any point.
Nondeterminism is a generalization of determinism ,so every deterministic finite automaton is automatically a nondeterministic finite automaton. The different between a deterministic finite automation and a nondeterministic finite automaton.
1- every state of always has exactly one exiting transition arrow for each symbol in the alphabet but the nondeterministic violates that rule.
2-In DFA, label on the transition arrow are symbols from the alphabet .this NFA has an arrow with the label ? , an NFA may have arrows labeled with members of alphabet or ?. Zero, one , or many arrows may exit from each state with the label ?
Nondeterminism may be viewed as a kind of parallel computation wherein multiple independent "processes" or "thread" can be running concurrently. when the NFA splits to following several choices, that corresponds to a process "forking" into sveral children, each proceeding separately. if at least one of these processes accepts, then te entire computation accepts.
Another way to think of a nondeterministic computation is as tree of possibilities. the root of the tree corresponds to the start of the computation. Every branching point in the tree corresponds to a point in the computation at which the machine has multiple choices. the machine accepts if at least one of the computation branches ends in an accept state. as show below.