Sucralose is an artificial sweetener that was first introduced to the world in the 1990's. In the US it is commonly sold under the brand name Splenda. It is about 600 times sweeter than sucrose. It is highly water soluble and can readily withstand baking and long storage, thus making it a very versatile and useful sweetener. It is different from other artificial sweeteners in that it actually is a sugar molecule but the human body cannot digest it so it passes through the digestive system without adding any calories.
In terms of structure, sucralose is nearly identical to sucrose (table sugar). The only difference is that three of the hydroxyl groups have been replaced with chlorines. I cannot draw the structure here but it is basically a glucose and a fructose molecule connected by a glycosidic bond. That means there are two six membered carbon rings (with one oxygen each) connected by an oxygen atom. Also, there are numerous hydroxyl groups bonded to the carbon atoms. The chemical structures for sucrose and sucralose are seen in the links below.