Benediction: An act or pronouncement of blessing. The Aaronic benediction was given to Aaron and his sons as a part of their ministry in God's behalf toward the people, and is epitomized as a putting of God's name upon them, (Numbers 6:22-27). The New Testament parallel is the apostolic benediction, (II Corinthians 13:14) which reflects the progress of revelation by its emphasis on the Trinity. Other passages, notably Ephesians 3:20-21, Hebrews 13:20-21; and Jude 24-25, are often treated as benedictions by members of the clergy.
The question is whether these are true benedictions or whether they are prayers. In the benediction the minister acts on behalf of God in pronouncing a blessing upon the congregation, whereas in a prayer he is the representative of the people. 
Since the benediction is the last part of a service
it is often the person's favorite part of the service.
Which benediction does your church/fellowship
use at the end of their worship services?
What benediction do you like best?
What purpose do they serve in your opinion?
 Evangelical Dictionary of Theology, ed. by Walter A Elwell (Grand Rapids, MI: Baker Academic, 1984, 2001), p. 148