What is each side of a 4-sided grater for?

To answer in the language of the question asked:

• Medium holes with a cutting edge on bottom (look like large raindrops) : used for shredding.
• Small holes with cutting edge on bottom : used for shredding when you want it finer than the larger size.
• Outward protruding holes with spiky edges on all sides : used for grating.
• Wide holes that look like a smiley : used to slice things to an even thickness.

As for recipes ... I generally don't use the slicing portion too often, as I can get fairly consistent slices with a knife, but if you're not so skilled, it could be used to slice potatoes for an au gratin (might need to slice them in half first, is the slots aren't wide enough to fit the whole potato), or to slice firmer cheeses. It can also be used for slicing cabbage for coleslaw (again, once cut down to fit), cucumbers or carrots for salads, etc. As the blades aren't razor sharp, there are some softer items (eg, tomatoes) that it just won't work for, that you'd have to do by hand or get a much more expensive mandoline.

The grating side I only generally use for hard cheeses, when I need a more powdery texture than I can get with the shredding sides. I've also used it for zesting citrus (although it only works in large quantities, as you end up losing about 1/2 a lemon to the groves and it doesn't release without a brush**), and I've used it for pulping carrots (was mixing them into a sauce, and I didn't want identifiable bits)

The shredding sides are the ones I use the most, with the choice of side dependent upon what size I want the resultant shreds. I use it for firmer vegetables and fruits that I'm baking into breads (zucchini, carrots, apples), potatoes for hash browns, medium cheeses for firmer cheeses (when I want this texture), etc.

Although a food processor can be used for this task, you have to consider a couple things (besides initial cost & space it takes up) : it's really easy to go and shred lots of cheddar cheese in a food processor, but it cramming all in there and fusing back together from the force and heat, defeating the purpose. Chilling the cheese helps, but you also need to keep dumping the work bowl out. If you have a strong arm and a small food processor, a hand shredder might actually be faster and give better results.

When using a shredding disk for firmer things, you do more damage than by hand, resulting in lots of liquid being given off. Sometimes, this is better ... I have a potato kugel recipe that comes out very light as I can get more of the liquid out after having gone through the food processor ... so you may want to try both tools (if you already own them both) to see which one gives you better results.

** ... I've heard you can wrap it in plastic wrap, use the grater, and then pull the wrap off to get it to release; I've never tried it, in part because I now have a microplane grater, but also because I'd be afraid of getting bits of plastic in the food. I also want to say that I saw the trick the context of pulping ginger or garlic, but it's been long enough ago that I don't know that I can trust my memory

I don't know that there is any universal standard for box graters.

Mine, at least has:

• Large holes—suitable for shredding medium density cheeses as for pizza and similar tasks

  Typical box grater showing large hole side (on right):

  

• Medium holes—suitable for smaller shreds, such as making potato hash browns. Might also be used in some cuisines for grating onions.

• Small holes—probably intended for hard cheeses like Parmesan; or garlic and ginger, or similar.

• Slicing slots—intended for making sliced potatoes for gratins and similar tasks.

  Typical box grater showing slicing slots (left) small holes (right):

  

In my opinion, today, there are better tools for all of these tasks. Food processors, of course excel at many of them. Manual micro-plane type graters do far better for ginger, garlic, and Parmesan. Mandolins are better at slicing, as are food processors with the proper blade. I haven't used a box grater in many years because it is almost never the best tool in my kitchen for a given job.

I use the side for slicing as much as the large grating side for shredding. A raw sweet potatoe sliced using the side with the single slicing blade, toss with oil, salt and pepper and spread onto cookie sheet. Bake for about 10 minutes at 400. Great side dish

Just last night I used the small grating side for zesting a lemon; it worked out great just like I see on the Food Network. I don't yet own a microplane so the cheese grater was my only option. I'll definitely use it again until I purchase a microplane.

I use the smiley faces for thinly slicing onions I want to include in a sauce or stew. They come out really thin and a little mushy, so I don't use them for salads

One extremely important application of a grater is for horseradish, the big grates way to coarsely, the side grates makes a mush. The small grates makes your horseradish perfect for mixing with dill, putting it on your potato salad, putting it on your salmon, your tuna, your BLT, your BBQ, your breakfast cereal.