The year you turn 71 is the last year that you can shelter money in an RRSP without taking any of it out.
By the end of the calendar year in which you turn 71 you have to either withdraw all your RRSP and pay tax on it (generally a bad idea) or you have to turn the RRSP into a RRIF. If you have any amount of money, the best plan is to turn the RRSP into a RRIF.
With a RRIF there is a required withdrawal each year. The required amount is what you will pay tax on, whether or not you take it out. My recommendation is that you take out the required amount at least, each year.
Generally, my recommendation is that if you are older than 71 you should be spending your retirement money – this is, after all, what you saved it for!