SSA is the basic Social Security Benefit. People who qualify for this program have paid into the system by earning enough work credits through their lifetime and have reached full retirement age. People may opt to draw on their SSA benefit as early as age 62, but will receive a reduced benefit.
Social Security Disability, or SSD, is similar to the SSA benefit in that a person must pay into the system to earn enough work credits. However, due to a long term disability, the person is unable to continue to work. In order to obtain SSD a person must apply for the benefit through Social Security. Many people are declined the first time they request SSD and may appeal the decision. Although it is not required, consulting an attorney may improve the appeal success and timeliness.
SSI is Supplemental Security Income. This program is for people who are low income and are age 65 or older or are unable to work due to disability. To apply for this program, a person must contact Social Security. It is important to note that unlike SSA and SSD, where a person has paid into the program and the benefit is an entitlement, SSI is a program that has income and resource limitations and is not an entitlement. Failure to stay within the eligibility requirements will result in a reduction or termination from the program. Social Security Web Site