Social Security Disability, or SSD, and the Supplemental Security Income, or SSI, are two separate programs of disability under the Social Security Administration. Both offer disability benefits; however, the qualifications are slightly different. Under SSD, you have to have worked long enough and paid in enough taxes to earn enough credit to qualify for that benefit. Generally speaking, it's a better benefit, with a high monthly benefit, and you may receive Medicare benefits, as well. Under SSI, it tends to be a more limited benefit. You have to financially qualify by having a lack of resources and low family income, and you may be limited to Medicaid. Those are the primary differences between the two plans.