Tacking is used for a variety of reasons, such as holding a seam in place until it is sewn properly, or transferring pattern markings onto the garment.
Tacking is used in a variety of ways; one of the most common uses is to easily hold a seam or trim in place until it can be permanently sewn, usually with a long running stitch made by hand or machine.
X-shaped tacking stitches are also very common on the vents (slits) of the back of a man's suit jacket, or at the bottom of kick pleats on a woman's skirt.
[1] Brand labels are also loosely basted on the outer edges of the sleeves of outfits as well as women's winter coats, intended to be removed after purchase.
They are meant to help customers to easily identify the brands in the store without reaching into the collar.