Stevia is a natural, alternative sweetener to sugar. It is from an herb plant that grows primarily in the country of Paraguay, located in South America. The properties of Stevia are somewhat paradoxical, as in its raw state, it tastes quite bitter. It only becomes a sweetening agent if it is heated. The use of Stevia and other natural alternatives as a sweetener has been a controversy in the United States. Until recently, labeling Stevia as a natural alternative "sweetener" was actually forbidden by the Food and Drug Administration. Meanwhile, Japan has allowed the mass use of Stevia as an alternative sweetening ingredient for years.
Stevia is usually available for purchase from health food retailers, both in physical stores and online. It comes in a powder form and as a liquid. The powder form usually is a combination of granulated Stevia and other ingredients that sweeten and help with the product's composition and dilution into the food you wish to sweeten. In purchasing the powder form of Stevia, you need to carefully check what you are really buying. The product may be composed more of other things, with Stevia being only a lesser ingredient. These other ingredients might not be so healthy or desirable, so check the ingredients listing. Also, contrary to some marketing claims, powdered forms of Stevia usually are not suitable to use like you would granulated sugar. In other words, you can't just sprinkle it on food such as cereal and eat it. However, it does work well when heated, such as putting it into a hot drink. If the powdered Stevia does work well without heat, it almost definitely has other ingredients in it.
The liquid form of Stevia is usually a more pure product, absent the mixture of other ingredients. However, you still need to check into the strength of the liquid solution and its freshness. Liquid Stevia will definitely be quite bitter if you use it without somehow cooking or heating it. Also, even when heated, if you use too much of it, you will also get a bitter taste as a result. Another variable in results is based on when you mix it into the food you wish sweetened. Although there are some tested published recipes using Stevia, you will have to experiment with quantity and timing to get your desired results.
Stevia is a healthy and natural alternative to sugar and sugar substitutes. Be prepared to experiment with it and you will likely make it a staple in your kitchen.