Void means it never happened
If something Is void then it never legally happened.
In the context of a contract it means there never was a contract that a court can enforce.
This can lead to perverse outcomes. For example, if I supplied you with widgets under a void contract, contract law will not force you to pay for them nor force you to return the widgets. Equitable remedies may be available to me (or not) but contract law won’t help.
Voidable means someone has the right to declare it void (q.v.)
The contract is enforceable by the person who has that right but only by the other party if the person with the right to make it void declines to do so.
For the widget example, if I can make it void, I can enforce the payment provision on you but if you can make it voidable I can only get payment from you if you choose not to make it void.