US terms are used for the stitches in this text.

Crochet post stitches are really useful for making different textures on your work, like for example cables or ribbed texture.

Crochet post stitches are not worked in the ordinary top loops of a stitch . They are instead worked around the post of a stitch.  Any stitch can be worked as a post stitch but I will show you the difference between an ordinary double crochet, a front post double crochet and a back post double crochet below.

Ordinare double crochet

When making an ordinary double crochet you insert the hook in the top loops of the stitch, see picture 1 below. The result after finishing your double crochet(s) are shown in the two last images below.

Front post double crochet

When making a front post double crochet you insert the hook from the front of your work around the post of the stitch instead of the top loops, see picture 1 below. The result after finishing your front post double crochet(s) are shown in the two last images below.

Back post double crochet

When making a back post double crochet you insert the hook from the back of your work around the post of the stitch instead of the top loops, see picture 1 below. The result after finishing your back post double crochet(s) are shown in the two last images below.