Believe it or not, for water to boil at 100 Degrees Celsius, it needs a seed bubble of gas to start boiling. If there is no seed bubble, then the water can "superheat", reaching temperatures significantly above boiling point. If a bubble is then introduced, such as by bumping the container and creating a small splash or exposing the dry air holding sides of the vessel to the super heated water, a chain reaction can occur and a significant portion of the water can all turn to steam simultaneously: possibly "explosively". This is actually quite hard to do in the real world, as almost all of our containers have small scratches that hold tiny amounts of air that we cannot see. In addition, when heating water from a tap for example, The solubility of gases falls as temperature rises, so bubbles of dissolved gas precipitate out of the water as it gets towards boiling: creating seeds. In the Lab though, Pyrex glassware may be brand new, and the insides of containers still super smooth and unscratched. If you somehow superheat a solution, it could explosively boil throwing the incredibly hot (possibly toxic/Acidic/Caustic) contents over yourself, other people, or onto places where you would otherwise not want hot chemicals. Boiling chips are a way of introducing seed bubbles, through the course surfaces and thus the amounts of air that fill the tiny gaps on the chips surface. I think that pretty much explains everything, If you have any questions, Ask away! Everyone else is free to add anything hey like if I stuffed something up or skipped something. Hope I helped!