The chain stitch (abbreviated ch) is the basis for almost all crochet patterns.
When you work in rows, your first row is a series of chain stitches, which is called the foundation chain. In order to begin the foundation chain you need to know how to make the slip knot.
When you start a new row you use the chain stitch.
Sometimes when you work in rounds you have to work a few chain stitches and join them together to create a ring.
How to crochet the chain stitch (ch)
Yarn over your hook, pull the yarn through the loop that is on your hook.