Padding stitches are the only stitches that use a third dimension of placement – behind in the meaning of “on the back side of” a special stitch.
These stitches use the free top loops of a stitch that was skipped for a special stitch in a previous round. They are made into the stitch behind that special stitch (without turning your work!). The special stitch stays in front. Flip the top edge of the work slightly down so that you can see the free / skipped stitch in the back. Sometimes the skipped stitch can be a bit hidden. Make sure you find the correct loops to work into.
Padding stitches increase the special 3D effect of an overlay crochet pattern and bring the skipped stitch behind the special stitch up to the level of the current round.
Wrapped in Jamie’s square, triangle and border patterns as well as most Heirloom and Afghan patterns use two different padding stitches (and occasional, especially explained variations of those) – hdcbb and dcbb.
hdcbb – technically this is a hdc_0-2-b, half double crochet behind the st 2 rounds below the next stitch
dcbb – technically this is a dc_0-2-b, double crochet behind the st 2 rounds below the next stitch