SSDI stands for Social Security Disability Insurance. It’s the type of benefit that you qualify for by having worked enough and paid in enough to Social Security taxes to qualify for that benefit. It is typically considered to be a better benefit than Supplemental Security Income (SSI), because you may receive more in monthly benefits, and you may qualify for Medicare in addition to/or instead of Medicaid. Some individuals may qualify to receive both SSDI and SSI benefits.