Basting stitches are long removable stitches sewn either by hand or machine. A basting stitch is a really good technique to know. For example, when tailoring and you need to fit a garment or hold a dart, or when sewing slippery or stretchy material, or even to hold a zipper in place.
For machine basting, start with your straight stitch.
Then your longest stitch length.
I tend to use a contrasting thread when I baste, this allows you to easily find the stitch + not rip out your actual seam. Simply stitch your fabric.
Then when you are done with the project, you should be able to pull the stitch right out of the fabric.