In 2/2 ribbing, if I end the row on a knit, do I start the next row on a purl? I get so confused with this.
Thanks 
Think of it this way… the stitches have two sides… one side is a knit and the other side is a purl. So if you end with a knit you would start with a purl. You’ll hear this a lot and it’s good to learn… when ribbing “knit the knits and purl the purls”.
Take a good look at what your stitches look like and here’s a picture of them I took to help.
Its hard to answer your question (except as knit the knits, purl the purls, because the answer depends on the count…
if your 2 X 2 ribbing is:
VVvvVVvvVVvvVVvvVV(starting and ending row 1 with KNITS)
then you start (and end) row 2 with PURLS.
but if your ribbing is
VVvvVVvvVVvvVVvvVVvv (staring with Knits, ending with Purls!) then you start row 2 with Knits and end with purls
*sample 1 (start and end with KNITS on row 1) is more common, but not universal.
and since you didn’t indicate which type of 2 X 2 ribbing you are doing, there is one single answer!
Learning to read your knitting is the best skill you can develop. Ribbing with its regular pattern is a good place to learn.
*starting and end with knits is common for sweaters and other items with a seam. when the egdes are put together, you get 4 knits in row… but seam with mattress stitch, and 2 of those knit (one from each edge) disappear into seam, leaving 2 knits… (and the edge has a perfect 2 X2 finish)
THis also depends on if your knitting in the round or knitting flat.
Niffer did indicate what type of 2 x 2 she was doing:
so the short answer is start with a purl.
I agree that learning to read your knitting (as Jan’s great pic illustrates) is a skill you will never regret, but somehow the whole business of ribbing always makes me pause and question if I’m doing it right, especially after doing a bunch of socks and then going to flat knitting.