In the Sunni tradition, what exactly is the role of an Imam?
The word Imaam in Arabic means a guide. Its relevance changes depending on the context of the word being used.
If we're discussing prayer, it would mean someone who leads the prayer. If we're discussing governing, it would mean the leader of the state. But the role is to be the guide and lead.
The Prophet Mohammed used Imaam in these contexts.
Imam have many roles :
source : www.islamweb.net also my reallife (i'm Muslim )