Growing miniature trees is only a small part of what the art and discipline of bonsai is all about. The word "bonsai" in Japanese is translated as small tray (bon) to plant (sai) or "to plant in a small tray", but if you have only planted a tree in a small tray, or pot, you do not have a bonsai.
There are multiple layers to Japanese bonsai. For some there is a spiritual aspect, in addition to the gardening and the artistic aspect, that must be be brought together to make a true bonsai. When you have created a beautiful tree it is something you can be proud of. Can you see how a bonsai cannot be created if any of the dimensions are missing?
Almost anyone can learn to be a good gardener. A successful bonsai gardener must first be a well-educated and successful gardener. There is much more to bonsai than planting and watering your tree. He must understand the role of a tree's roots, it's trunk, branches, and skin. A bonsai artist must be a bit of an arborist. He will need to understand the light and humidity requirements of his trees. Your bonsai trees will suffer unless you are able to attain and bring all of this knowledge to your bonsai project. And, without this understanding of horticulture it would be difficult, if not impossible, to apply techniques that are part of the artistic dimension of bonsai.
The third element of bonsai, the element that creates a miniature replica of a tree that almost precisely resembles a tree in nature, is the artistic element. Like a sculptor that can see a statue inside the block of granite, a bonsai artist must look inside the bonsai tree to understand it's essence, and then train and shape the tree into form. There are many forms that a tree can take in nature, and they are replicated in the classic styles of bonsai. The bonsai artist may employ several different techniques, including pruning, wiring, grafting, and pinching to shape his bonsai in one of the traditional bonsai styles.
The final dimension of bonsai is the philosophical or spiritual dimension. There must be a connection between the bonsai artist and nature. Some relate the philosophy of Taoism and Buddhism to bonsai, while others relate it to Zen philosophy. A true bonsai cannot be created in the absence of a true connection and understanding of the natural world, regardless of the philosophy.
People who work with plants and trees to create Japanese bonsai most assuredly develop a broad appreciation of nature as they do their work, and understand that they are creating a thing of beauty. luckily, even people who don't completely grasp the multiple elements of bonsai can still be affected by its beauty.