Stranding is often used with “intarsia” knitting. But there is a difference. Intarsia, the knitting of pictures or motifs, is usually done in the flat. Stranding applies to both intarsia and fair isle type knitting. Think of fair isle as a pattern that repeats all across a row or round of work. Check out this gorgeous sample from Color ‘n Cables
Here are two terrific videos to show you how to “strand” unused yarn across the back of the work when you are doing colour work such as that found in the penguin sweater or the nursery block sweater.
The first video shows you how to strand on the right side of the work. The hardest part of stranding is to keep the tension even so that the front of the work doesn’t pucker. As you watch look for ideas that will help you avoid puckering.
The second one shows you how to strand on the wrong side of the work if you are knitting in the flat.
The Color ‘n Cables blog has other discussion on fair isle technique helpful to experienced knitters who are tackling classic fair isle knitting.