That's about Medicare Advantage Plans (Aka Medicare Part C), but while some these plans are good, some may not be. I suggest you go to Medicare and find one they recommend.
By the looks of it, they're pushing Medicare Advantage "giveback" Plans. It's a "Mail Piece" as it's known in the junk mail industry. Also, a bit deceptive, as it's designed to resemble an official document, meant to fool you into opening it and getting you to respond. Essentially, these plans pay back some or all of the monthly premium you'd otherwise pay for Medicare Part B, which is typically deducted from your Social Security benefits.