What is the difference between SSDI and SSI benefits?

• Social Security Disability Insurance (SSD or SSDI): This program is for disabled people who have worked and paid into the Social Security system, and their surviving disabled spouse and children. Disabled individuals who do not meet the work history requirements are not eligible for benefits under SSD. This program is not means-tested.
• Supplemental Security Income (SSI): These benefits are available to disabled people who have not worked and paid into the Social Security system. Eligibility is based on need alone, and eligibility depends on the applicant’s income and assets. Disability requirements for SSI are the same as for SSD.