“Levites are the descendants of the Tribe of Levi, one of the twelve tribes. In addition to Levites, the Kohens (priests) are also descended from Levi. Both are integrated in Jewish and Samaritan communities, but keep a distinct status.”  https://en.wikipedia.org/wiki/Levite

Much more information can be found here: http://www.biblestudytools.com/dictionaries/bakers-evangelical-dictionary/levite.html

The dictionary meaning of the word says: “uttered at the end of a prayer or hmn, meaning ‘so be it.’.

In the biblestudtools.com website it says,  “means to take care, to be faithful, reliable or established, or to believe someone or something.”

For more information see their site at: http://www.biblestudytools.com/dictionary/amen/