Social Security Disability is a government program that provides financial support and medical insurance for people who are unable to work. If you are working, as a general rule, you are not eligible for Social Security Disability. In fact, if you return to work within one year of your original illness or injury on a full-time basis, generally you are not entitled to benefits at all.
But Social Security Disability is very complicated. There are times you can do some work and still be eligible for benefits. At the same time, some things you might not consider to be 'work' are deemed as work by Social Security.
Instead of using the word 'work', Social Security calls it Substantial Gainful Activity, or SGA. Substantial means something that is more than just a little bit. If it requires significant use of your body and mind, then it is substantial. 'Gainful' means for pay or profit. Even if you don't earn very much or even if you earn nothing at all, it is still gainful in you intended to earn something. 'Activity' is just another term for something you do. I you are performing SGA, you are not eligible to get Social Security Disability.