A primary beneficiary is the person who will receive your life insurance's death benefit payment in the event of your death.
A contingent beneficiary is a back up plan - in case the primary beneficiary person doesn't survive you.
You can name several primary beneficiaries and several contingent beneficiaries, just specify the percentage allocation among them of your death benefit payment.
Part B - what if you have multiple primary beneficiaries, and none of some of them don't survive you?