This is the amount you will receive based on your earnings record. Generally speaking, you need to have worked for at least 10 years before you can qualify for Social Security retirement benefits on your own. The 10 year requirement does not apply to Spousal Benefits.
Spousal Benefit - Married:
One spouse may claim a benefit based on his/her spouse's benefit. The spousal benefit is equal to 50% of his or her spouse's Full Retirement Age benefit. For the sake of example, let's look at Jack and Jill Smith. Jack is full eligible for Social Security benefits and his Primary Insurance Amount is $2,000/month. Jill was a stay at home-mom and does not qualify for Social Security benefits on her own. Nevertheless, she can claim a spousal benefit equal to 50% of Jack's $2,000 benefit when she is at Normal Retirement Age.
Spousal Benefit - Divorced:
If a couple were married for at least 10 years and they divorced from each other, a still divorced spouse (spouse #1) is entitled to a spousal benefit equal to 50% of ex-spouse #2's Primary Insurance Amount. This is true even if the spouse #2 is remarried. Furthermore, claiming a spousal benefit does not penalize either party in any way from Social Security's perspective.
A survivor may claim against a deceased spouse's benefit. At the survivor's Normal Retirement Age, this benefit is equal to 100% of the benefit the deceased would have received if still alive at his or her Normal Retirement Age.