In afghan crochet, each row is worked in two halves: the first half is worked from right to left and the second half from left to right. Work is never turned.
After the starting chain is completed, the first row is worked by inserting the hook in the chain, pulling a loop from the free end of the yarn, and inserting the hook in the next chain without working the loop off the hook. At the end of the row, you will have as many loops on the hook as there are stitches across. In the second half of the row, you will work the loops off the hook.
This type of crochet creates a dense fabric with a definite front and back side. It is ideal as a base for cross-stitch.