What’s The Difference?
Some persons will argue that a steam boiler and a steam generator is the exact same thing while others will tell that they are similar but very different. The fact is that whether it is termed as a generator or a boiler, they are both machines that apply heat to water in order to create steam. This is the same effect that can be noted when you put a pot of water on to boil. The difference in definition is often attributed to the diverse pressure levels of older and newer boilers. In essence, some may argue that boiler machines with low or intermediate pressure levels are boilers, but if their pressure level rises above 2000 kilo pascal, some people will tell you that it is not a steam boiler but rather a steam generator.
Steam Engines
Now that we know the difference or rather lack there of, depending on where you stand on the subject, we can now move on to where these mechanisms are needed. We have already discerned that they are used when steam is required, but their type and size will be determinant on the job that they are needed for. You have more than likely heard about steam engines which are generally mentioned when ancient locomotives are being discussed. However, with the onset of electricity and diesel oil, steam engines for trains are pretty much a thing of the past.
Below is an illustration of a fire-tube boiler which is used in a steam engine:
http://science.howstuffworks.com/transport/engines-equipment/steam2.htm
Usages
In recent times, steam generators are used for multiple purposes and in diverse environments. Some are used in heating mechanisms for household use, they are used in humidifiers, they are used in industrial plants and even for sterilization in some settings. Contemporary boilers and generators are made to utilize fuel or electricity to administer heat to the water until it reaches the desired temperature to produce steam; the steam is then used to power additional machines which in turn generate electricity for other purposes. So in conclusion, it is safe to say that a technology that has been implemented from as early as the 1900s is still being effectively used today.