The creation of additional plants through division, encouragement of keiki formation, or any various meristematic techniques, but not via seed.
Plants can reproduce in two ways. In the first, the old fashioned way, seeds are produced that include genetic material from two plants. The seed is planted, and it grows. The other is vegetatively. Some kinds of plants, especially climbing ones will produce roots if their stems are buried. This is a simple and naturally occuring kind of vegetative propagation. More often woody pieces of garden plants are trimmed from a plant, dipped in rooting hormone and kept under just the right light, temperature, and humidity conditions. The cutting sprouts roots and leaves and before long is a viable plant. This is the way virtually all commercially available roses are propagated.