What are the different applications for differently shaped wooden spoons?
Number five is a folding spoon. It is made for folding flour into light foams without overmixing, for example when making Genoise. The big hole makes the mixing easy, and the shape is good for scraping the bottom of a round bowl. 

As Dave Griffith already said, 3 and 4 are for stirring stuff in pans and skillets (making roux, cooking off the liquid in tomato or pepper puree for ajvar-like condiments). They prevent the contents burning on the bottom, because they remove the very heated layer from the bottom and let cooler liquid flow in. 

The slot in spoon 2 make it a poor replacement for a skimming spoon. Normally, you want a bigger perforated spoon for that, with bigger holes. Also, I think metal is a better material in these cases, it isn't so good to put wood in boiling water. 

Number 1 is useless in cooking. Historically, these spoons were made for eating. When they were big enough, housewives just used an eating spoon for stirring, because this is what they had at hand. Nowadays, people don't eat with wooden spoons, but the tradition persists in that they continue using the traditional shape for stirring. This is a bad idea. It has the wrong shape for flat-bottomed pans and curved bowls. There is no use case for which the other spoons aren't a better fit. Maybe getting flour out of a package into a bowl, but being much flatter than an eating spoon, it is inferior also for this use.