That's not exactly right, brenda. A good point, but not what "pooling" is.
Pooling is when you use a varigated yarn and because of the dying pattern, you can sometimes get a color pattern in the finished fabric in which you have noticable blotches of one color, or zig zag shapes of color. Ideally, with a varigated yarn, you want a nice mottled, evenly varigated finished peice. To avoid pooling, do as they say and knit 2 or 3 rows from two separate balls of yarn. To varigate it further, you can knit in a fair isle/stranded fashion, knitting 3-5 stitches from each ball, but this will use more yarn.