An eruv techumin (Hebrew: עירוב תחומין mixed borders) for traveling enables a Jew to travel on Shabbat or a Jewish holiday. He prepares a food prior to Shabbat or the holiday on which he plans to travel farther than is normally allowed on such days. (This is unconnected to the method of transportation which is being used, all of which - other than walking - are forbidden on such days.)
Normally, one can walk anywhere in his city or town on such days, but only within that area and up to 2000 cubits past the city limits. (The definition of "city limits" in Jewish law is beyond the scope of this article. Suffice it to say that it relates to the area which is actually populated, and not to the political borders of a municipality.) If one needs to travel farther than that, he can leave some food in a certain location prior to that holiday or Sabbath. This will temporarily establish his home as at the location of the food, allowing him to travel 2000 cubits from the food. There are many other details beyond the scope of this article.