please explain what the letter is?
The benefit verification letter , sometimes called a benefits letter , or a Social Security award letter , serves as proof of your retirement , disability , Supplemental Security Income SSI , or Medicare benefits
what can i use my letter for?
It also serves as proof that you have applied for benefits or that you have never received Social Security benefits or SSI  You may also use your letter as proof for loans , housing assistance , mortgage , and for other income verification purposes