Structurally, the function of tubers and bulbs is the same: They are both underground storage systems that produce flowers and foliage by stockpiling nutrients for plants. Here's how they differ: a bulb is made up of modified leaves, whereas a tuber is a modified stem. Bulbs and tubers have evolved over time to withstand harsh conditions by entering into a period of dormancy. During this period, they draw upon their stored nutrients for survival.
An onion is an edible bulb. Cut one open vertically, and you'll see that its sections are modified leaves. The base of the onion would be considered its root. Other examples of bulbs include tulips, daffodils, amaryllis, and hyacinths. To multiply a bulb, cut it into pieces and include a section of the base with every piece. To plant a bulb, dig a hole three times as wide and three times as deep as the size of the bulb. Plant most bulbs pointy side up.
A potato is a good example of a tuber. Cut it open, and you'll see that it is fleshy and starchy; in general, the volume of a tuber is greater than that of a bulb. Elephant ears are tubers that can grow to a height of six feet. To divide a tuber, cut it into sections; make sure you include an eye in every section.