The conversion Designation means that you can switch out between .22lr & .22 magnum cartridges by swapping the cylinders (Both .22lr & .22 magnum included)

Hi Gerald and welcome. Conversion or Combo indicates two separate cylinders are included, 22 long Rifle and 22 Magnum that you can convert between the two for firing the power level you need. Cheers and stay safe!

Good morning Gerald. The conversion means this comes with both the .22lr and .22wmr (magnum) cylinders, so you can shoot both .22lr and .22wmr.
Stay safe & have a great day!