Frogging it a slang term used for anytime you have to undo your work. It comes from saying "Rip it, Rip it".
Unpicking indivdual stitches can work if you only have to go back a few stitches. But if you have to go back several rows, ripping it out -- or Frogging -- may be the way to go.
Some people put life lines in every few rows so if they do have to frog, they just frog to the life line and then just pick up the stitches on the life line. Others are comfortable frogging to a row before the mistake then unpicking the row that needs correcting. Many ways to frog