If you are a reservist, you get 15 points per year just for being affiliated with a reserve component. You typically get 4 points for every drill (two days per month), 12-15 points for your annual tour (two weeks per year), and 1 point for every day of active duty (deployment, active duty for training, active duty for special work, etc.). You can also earn additional points by doing correspondence courses. You need at least 50 points in a year for that year to count toward the 20 years to earn a retirement. The more points you have when you retire, the higher the percentage of your base pay you will receive as your pension when you turn 60.
This is not true. You still get 15 points per year in the IRR, you can still do correspondence courses for points, and it is possible to get orders to participate in annual tours if funds are available. In addition, you could affiliate with a Volunteer Training Unit (VTU) and drill for points without pay. It is very possible to earn the needed 50 points for a qualifying year while in the IRR.