Social Security Disability Insurance (SSDI) pays benefits to you and certain members of your family if you are "insured," meaning that you worked long enough and paid Social Security taxes. Under this program monthly payments are based on the individual’s earning record, which is on file with the Social Security Administration.
Supplemental Security Income (SSI) pays benefits based on financial need. It provides monthly payments to individuals who have either never worked or have insufficient credits on their earnings record to qualify for SSDI. SSI recipients are typically required to have limited financial resources and assets that do not exceed $2,000.
These programs are both administered by the Social Security Administration and the disability criteria are the same for both. In order to qualify for SSI or SSDI, an individual must "have an impairment or a combination of impairments that preclude substantial gainful work activity that is expected to last a continuous period of 12 months or longer or that is expected to result in death."
Tips for the application process:
-- When you go to apply for benefits, take a copy of your medical records and a letter of support from your physician
-- Bring a list of medications you are currently taking
-- Submit a copy of your most recent tax return along with a recent paycheck stub
-- Make sure that you can provide appropriate documentation such as your Social Security number and the name, address and phone number of your treating physician(s)
-- Get the name of a specific case worker who will be reviewing your file
And don't get discouraged if you are turned down the first time. This happens to a lot of people (something like 50 or 60% are denied the first time) and it's normal to file an appeal.
More info here:
http://www.ssa.gov/disability/
or you can call 1-800-772-1213