Rib structure belongs to the double jersey structure, wherein a course you can find technical front and back loops alternatively. double bed. Widely popular in v bed machine. This knit same course has technical front and back loops, All the needles making loops on both beds is called full rib.
And 1×1 rib knit means only one needle is active and the other needle is not active on both beds. It means alternative needles are active rest needles are just sitting ideal they are not part of loop formation this is called 1×1Rib knit.
2×2, two ribs in both the beds two needles are operating two are sitting ideal, similarly, on the back bed, two needles are operating two needles are not operating 2×1 rib-knit indicates on both the beds you are making two loops one needle is not acting. If you see the front bed two are acting one is resting. Similarly, on the back bed, two are acting one is resting.