I don’t understand this RMD thing. There is nothing on my 1099R?

RMD stands for required minimum distribution. It is the amount of distributions you are required to take from your pension plan starting when you are 73 years old. Basically it is the amount you would have to distribute each year for the rest of your life expectancy in years to completely liquidate your pension plan. The purpose of it is to make you withdraw your pension money so you can pay tax on it before you die. It applies mostly to self-funded retirement plans such as IRA's and 401-K plans. If you are unsure if you are required to take a RMD or the amount to take, you should ask the administrator of your pension plan for help.

Why did you get  the 1099R?  What code is in box 7?  Is it for a pension?

It's whatever they send you. Say all of it is the RMD. If you have a RMD requirement it will ask you if it is the RMD. Say yes and enter the amount as the RMD amount. The pension doesn't need to calculate any RMD. Anything your pension pays you is considered to be the RMD. Traditional pensions automatically fulfill the rules of an RMD. So just enter the same amount in box 1 for the RMD for each 1099R.