While similar to common 'regular' onions, the Egyption walking tree onion produces a cluster of bulbs, both under the ground as well as at various locations up the stem. Rather than reproducing via seed, this plant can be cultivated simply by planting the small bulblets that form in the air.
At the end of the plan's life, if not harvested, the stems with aerial bulblets fall over, touching the ground and eventually taking root and forming new plants. This is how the onion 'walks'.
Starting plants from a bulb hundreds of times bigger than the actual seed gives it a much stronger start in life, allowing it to grow in more competitive situations, even allowing it to push up through quite thick mulch.
The edible part of the onion, the bulbs from under the ground, are much like shallots, being stronger in flavour and more elongated in shape compared to the more conventional onions most people are familiar with.