There is not much if any difference in either Endurance running or Ultrarunning it is just a matter of the words you use to describe something extra ordinary. Ultrarunning is probably a more specific way of describing a long run which in most cases would be longer than 50K (30 miles) in some ultra runs people would be running more than just one day. One of the more well know ultra runs with 6 days of running (apx. 151 mile/ 243K) would be Marathon Des Sables (MDS) which is to be held in the desert of Sahara.
Another race similar to MDS are the races made by the organization www.racingtheplanet.com these races are known to be held in different deserts such as Gobi desert in China, Sahara desert in Egypt, Atacama desert in Chile and Antarctica and all of them are set up with scenery one will never forget. These 6 days runs are classified as ultra running but could just as well be a race of endurance running and are often called Ultra Marathons.
Some people would classify half a marathon as endurance running where as for others it had to be a whole marathon to be classified as Endurance running. Looking ahead of things running a Marathon becomes more and more common. Running a Marathon 15 years ago would really be an accomplishment. Today more and more people compete on how many Marathons they have been running and not just on running one marathon and that is why endurance running within time will require longer and longer runs to be classified as endurance running for some people.
Never start out running longer runs than you have done before and never increase your running distance to fast. A good hint could be to increase your distance with no more than 10-15% but remember people are different so for some it might be less and for others more. One thing is for sure if you increase the distance of your runs to fast you will end up with injuries. It might not be the same day but over time you will run into problems because bones and muscle tissue does not get as strong as fast as your condition. That is why you might feel breathing goes good and that you feel you have an overload of energy and then the tough part is not to increase too much at this time. It takes time to be good and there are no legal shortcuts – just like anything else in life.
Anybody not in shape or not fit for whatever running goal they set out to reach would see 10k, a marathon or longer as an endurance run and that is why running and especially running the longer runs requires so much preparation with training, the mental part, how to eat and hydrate right and for some endurance races even the equipment. In the end it is all a matter of the small things that adds up to make a perfect performance. Endurance running is like many other things in life – A matter of experience – When you know how to do all the little things the right way, you will have an easier time to reach your goal without all the beginner mistakes.