The cow hitch (or lark's head) is used to attach a rope to an object.
The cow hitch is made of two half-hitches tied in opposing directions. (the clove hitch is two half-hitches tied in the same direction).
The common alternate name lark's head is a literal translation of the French name for the knot, tête d'alouette.
With the end
When tied using one end of a rope, such as when securing an animal's lead to a vertical post or stake, this knot was said to be more resistant to loosening than the clove hitch as the animal wanders around the post.
In a closed loop or strap
This knot is tied without access to the ends of the rope. It is also known as a strap hitch or girth hitch. It is used to attach luggage tags to a bag and connect loop-ended lanyards to handheld electronic equipment, as it can be tied without access to the ends of the fastening loop.
With the end, then secured into a loop
When tied by threading the end and then the end is secured to the standing part, the knot is known as a bale sling hitch.