Das Lied der Deutschen is the national anthem of Germany, with words written by August Heinrich Hoffmann von Fallersleben in 1841. The tune is by Joseph Haydn, who wrote it, paradoxically, to serve as the national anthem of Austria, not Germany. The original words were "Gott erhalte Franz den Kaiser" ("God Save Emperor Franz"), "Franz" being at the time (1797) the reigning Austrian emperor Francis II. Today, the tune is commonly known in most of the English-speaking world by the first line of its Fallersleben's first verse, Deutschland, Deutschland über alles, even though that verse is now rarely performed for reasons that are explained below. For more on the tune, see the Wikipedia article Gott erhalte Franz den Kaiser.
Fallersleben wrote "Das Lied der Deutschen" in a time when Germany was still a motley collection of quarreling kingdomss and principalities. He wanted to express his desire for a united, strong Germany. The line "Deutschland, Deutschland über alles, über alles in der Welt" can be understood in this context as an appeal to the German sovereigns to put aside all other projects and concentrate their efforts on creating a united Germany. At Fallersleben's time, this text also had a distinctly revolutionary, liberal connotation, since the demand for a united Germany was most often uttered in connection with demands for freedom of press and other liberal rights.
After these rights had been introduced after World War I, all three stanzas became the German national anthem in 1922. Not surprisingly, during World War II, when the Nazi government of Germany had occupied the bulk of the European continent by military conquest, it was easy for Allied propagandists to spread the view that the words "über Alles" advocated military aggression. As a result, the song still rings with menace today in the ears of many individuals. However, most would agree that, however valid the propagandists' interpretation may have been in regard to the Nazis, it cannot plausibly be made about Fallersleben's original text.
Banned after 1945 by the victors, the Deutschlandlied is again the German national anthem, but after the German reunification in 1990, only the third stanza was adopted as the national anthem of all of the unified Germany. The first two stanzas are not actually forbidden, but they are never sung on official occasions. Singing or using the first stanza may be perceived as an expression of right-wing political views.