I've noticed that some ordinance state:

ATTACK (FOCUS): Discard this card to perform this attack.

While others say:

ATTACK (TARGET LOCK): Spend your target lock and discard this card to perform this attack.

Does this mean that a focus token is not expended when attacking with those types of ordinance?

That's correct. For instance, Proton Rockets require that you have a focus token to fire them. You do not need to spend it, and can save it to modify your attack role.

Another good example is Blaster Turret. It requires you to spend a focus token to attack with it.

Thinking about it, there are also some missiles that only require a TL to fire; not spend it.

Basically, if the card doesn't tell you to spend the token, you don't spend it and can therefore use it to modify during the attack.

Thanks for the clarification.

Either type may or may not require you to discard the token to make the attack.

Where the two differ is that if a TL is required the attack must be against someone the ship has a TL on while on that requires a Focus is free to attack any ship. Subject to other targeting rules of range and arc of course.