A steek is an extra set of stitches that you include in your pattern so you can continue working in the round all the way up your sweater. This way you don't have to divide into front and back for sleeves or work the two sides of a neck separately.
When you're done with your knitting, you cut open the steeks and you have armholes and the front of the neck all done.
Now I'll pick up the stitches around the armholes and knit down to the cuffs.
Best part? No! Seaming! None! Nada!