In general, there are two kinds of kitchen island. The first is the large kind that may include a cook top and even a sink. These are immovable. The second kind is the smaller kind that more closely resemble a kitchen cart. these frequently have wheels but no cook top or sink. Either will benefit your kitchen with their extra storage and counter top workspace.
Large islands may require designs and planning. They may include plumbing and running water and electricity to the island. They may need permits for some of this work. These large islands can also have seating on one side and work area on the other and be used as a breakfast bar. 360 degree access make them so easy to use, that you will wonder how you ever survived without them.
More people have an interest in the second type than the first. They are easier on the budget. The versatility of a portable unit is a big reason also. The portable kitchen island is really just a larger version of the kitchen cart. If storage capacity is at a premium in your kitchen, then the portable kitchen island may be a better fit. They may have open drawers or pull out drawers or both. They have cabinets under the counter for storing larger items like pots and pans. On the sides you may find a handy towel rack, and some may come equipped with a spice rack.
Some kitchen islands may have a drop leaf. A drop leaf is a section of the top that can be added to make a larger table. This can be used for extra seating with the addition of some counter stools, or just give you added counter top space for preparing large meals. It gives you some always needed extra counter space.
The kitchen island is the best kitchen furniture for adding extra work space and extra storage space without going over your budget.