Social Security disability insurance benefits (SSD or SSDI) and Social Security retirement benefits are only available for individuals that have paid into the Social Security system. These benefits are funded through past contributions taken out of your wages by your employer over the lifetime of your working career. Retirement benefits are provided to individuals who are age 62. SSD/SSDI benefits are funded similarly to Social Security retirement benefits, but are for those individuals that suffer from a medical condition that lasting over a year or that will result in your death.
On the other hand, Supplemental Security Income (SSI) is paid to individuals who are older than 65 years old or who are disabled and have a particular income required for assistance.