This is the basic tunisian crochet stitch.

Starting with next chain from hook, insert the hook, yarn over, and pull up a loop. Leave that loop on the hook. Repeat this for each chain stitch. When you have picked up a loop for each chain stitch you will have completed what is known as a 'forward pass.'

Now we need to do the 'return pass'. You have a choice here: you can start with a 'yarn over pull though one' (i.e. chain 1), but it is not (in this instance) necessary. Sometimes it is useful, sometimes less so. Personally I use it for tss, but avoid it in most other situations because it makes the edge stitch wider, and the edge stitch generally does not match the pattern of whatever stitch you're using. A chain 1 edge on tunisian full stitch, for example, looks pretty awful (in my opinion). You may find that the chain 1 helps with tension issues if the end of your row is very tight.