Two by two rib (2X2 rib) is a very special rib. It is the most stretchy rib.
![2x2 rib sample 2x2 rib sample](/images/rib/2x2rib.png)
![back side of 2x2 rib back side of 2x2 rib](/images/rib/2x2rib2ndside.png)
Which is the right side? The pattern will probably tell you what they think is correct. It is generally easier to hide a seam when you are joining the purl stitches as those purl stitches recede.
The stretchiness of 2x2 rib makes it great for children's necklines where a larger than normal amount of stretch is needed. It is also frequently used in socks, particularly for someone with wide feet, large ankles, and or larger than average legs.