What is tang?
Tang is the metal part of any blade that is in the grip of the knife. Typically, to save cost, the blade is made so only the tip of the metal at the back end of the blade that will be covered by the grip. As an example, the majority of kitchen knives are partial tang knives. The best full tang knives normally designed for more adventurous usage such as camping, hiking, fishing or hunting.
Why do we need a full tang knives?
It depends on what can of usage (or abuse) you are going to use your knives for. For simple activities, cutting soft materials, half tang would be enough. Half tang also means that the knife will have a lighter weight. However for a severe usage as in military, hunting or fishing the best full tang knives you can get is recommended. Since the knife will have a metal backbone throughout the grip, the knife will be more durable thanks to the full tang shape. The biggest difference between the full tang knife an half tang knife is when the grip is shattered. Half tang blade will lose its function, but the full tang knife can still be used as a knife, just grip the tang. If it feels uncomfortable, just wrap the tang with clothing or ropes, you get yourself functional knives with a new DIY grip. This is very useful for a field repairs.
How to know which is the best full tang knives or it is just a partial tang knives?
Unless you put the knife under x-ray machine, you wouldn’t know. But normally full tang knives will state it out on the product descriptions since it is the best features people are looking for when buying knives. Half tang knives never actually clarify their tang construction. A simple tips to remember, full tang knife must be a fixed blade knife, a folded knife can never be a full tang knife.