It's easy to be confused - the term dutch oven has been so missused it's had for anyone to figure out what one is.
A REAL Dutch Oven is designed for use on a campfire - not on a stovetop or in an oven. It is made of thick cast iron, has three short legs on the bottom and has a relatively flat lid with a lip around it to keep coals from sliding off. They probably got their name from being made using the Dutch process of casting iron, and by heating from the top and bottom they acted like an oven.
Something else called a Dutch Oven is a camp oven ... again made from thick cast iron - no legs and has a domed lid with cone-shaped spikes on the bottom of the lid ... these collect condensation and help redistribute the moisture evenly across the pot. These can be used on the stovetop or in the oven.
Now, another pot that is often mistakenly called a Ducth Oven is a pot made from thinner cast iron and coated with enamel - like LeCruset. These are "French" Ovens ... if you look at LeCruset's website and you will not find the term Dutch Oven anywhere. These are also excellent for stovetop and oven.
And the others ... manufacturers who don't know what to call a 5 or 6 qt pot that is wider than it is tall just call them "Ducth Ovens" regardless of the material - because they are the same shape even if they share none of the cooking characteristics of a real DO.
Cast iron, and enamel coated cast iron, pots share one things in common ... cast iron is a POOR (slow) but EVEN heat conductor ... which is exactly what makes them so great for long, slow cooking - over a camp fire, on the stovetop or in the oven ... as the temperature around them changes they remain more constant than copper, aluminum, hard anodized aluminum or stainless steel.
Enameled cast iron doesn't have to be seasoned ... which is an advantage over regular cast iron ... plus it comes in pretty colors, it cost more, and is more prone to damage from thermal shock. LeCruset is the most famous French Oven - and the most expensive ... there are other less know brands that are IMHO just as good. But, like keltin said - check the oven specs to see how hot you can get it. Although the enameling process requires some really high temps - really thin enamel coatings are not always rated for higher oven temps.
What you get depends on what you're going to use it for and how.
Sorry ... calling every 5-6 qt pot a dutch oven is like scraping fingernails across a blackboard to me ...