This is the Timber Hitch. It's uses are varied, but the name gives away where it was developed. It is used mostly to use as a temporary attachment. The Timber Hitch is a very quick way to tie a rope to a log.
2 Half Hitches is the combination of a couple of half hitches, duh! It is mainly used to secure tent and dining fly ropes to stakes. It is used in marine applications as well.
The Clove hitch is mostly used to tie a rope to a secure object. It is also used to start a lashing of two poles together.
The Sheepshank is a knot used to shorten the length of a long rope when no slack is wanted laying around. An application may be on a rope monkey bridge for effect.