What is "meribah"

Meribah or "Mirabah" is one of the locations which the Torah identifies as having been travelled through by the Israelites, during the Exodus, although the continuous list of visited stations in the Book of Numbers does not mention it. In the Book of Exodus, Meribah is mentioned at the same time as Massah, in a context which suggests that Massah is the same location as Meribah, but other biblical mentions of Massah and Meribah, such as that in the Blessing of Moses, seem to imply that they are distinct.