If you are ever in church, you may be singing a hymn from a hymn book. You may notice that there are many different verses to that song. Usually the congregation will sing each verse to the same tune. This is because there are different verses to the song. This is a repeated section of a song with the same melody but different lyrics time.
The song my sound the same if you couldn't hear what the words were, but the words that are being sung would be totally different. Many times in hymnals the songs contain four or five or even more verses. Most of the time if a songwriter writes a song, there is only one verse to it.