Prayer brings us closer to God.  When we ask for things from God, even though God already knows what we want and need, we get merit (zechut) for the prayer.
Particularly in synagogue, a holy place, we must be always cognizant of God's presence and take special care to show respect to God in His house. This awareness is even more important than memorizing the halachot of prayer: those who speak in synagogue are showing disrespect to God as well as disturbing others and preventing them from praying with concentration (kavana).
The three daily prayer services--shacharit, mincha, and ma'ariv--are related to the three forefathers who instituted them.  They partly take the place of—and are modeled after--the Temple sacrifices.
If you find you have made an error in saying a blessing or prayer, you may correct your error without having to repeat any previous parts if you do so within 2.5 seconds.