An auger is effectively the same as a drill piece. The difference is that augers are much larger and are used to make holes in the ground. The size of the auger defines the size of the hole, although you will also have to consider the terrain you are digging into.
Earth augers are very good at making holes in soft, earthy soil. However, they are not so effective at making holes in rocky soil or if you are going deep enough to hit the rock level. That is why you should always test the soil to see what you are dealing with before you choose your auger.
Of course, if you are going into rock you will need rock augers. These are excellent for rocky terrain, deeper holes, and drilling boreholes, and similar.
Obviously, the larger the hole and the more difficult the terrain the more expensive the rock auger will be. But, in general, these are cheap and very effective tools.
The Power Head
Small augers can be fitted to a standard drill and work surprisingly well. All you need is a drill with enough power to keep the auger turning. However, if you are dealing with the larger augers you will need a dedicated powerhead. This is simply because the head of the auger is too large to fit into a standard drill.
Even though you are drilling a hole to plant a tree, you need to be aware that an auger can kick back and it can be a powerful movement. It kicks as it bites into the soil, being prepared for this will ensure the process is smooth and stays on track.
If you are planting a young tree then it is likely that the auger will remove enough soil to allow you to drop the sapling straight into the ground and leave it to flourish. However, if you are using an auger to plant a larger tree you will need to dig as well. The best approach is to dig a shallow hole as wide as you need it to be. Then, place the auger in the center and drill down a little, this will release the tension on the soil, allowing you to dig the soil out before using the auger again. It is much faster and easier than simply digging a hole.
You can then continue with the usual process of planting a tree and refilling the soil around its roots.
Augers are very useful but they can be a little daunting if you have never used one before. The good news is that they are easy to get the hang of. All you have to do is choose a spot in your yard to practice and then practice digging holes with your auger. You will find that a few practices are enough to get you started on the real thing and transform your yard with your new trees.