Polls are a feature for roles that have the Executive Role option enabled. The Executive Role option is a parameter for every role that sets the percentage of role-bearers (every person in the nation with that role) required to pass most commands.
When you execute a command that requires the rest of the rolebearers to agree it (most nation commands are like this) and your role has the Executive Role option enabled, it will automatically create a poll for that command to be executed. Other role members have 6 hours to vote on the poll (the hours necessary can be changed with
/nation set). If the percentage of members that voted for the poll exceeds the required percentage, the command will be automatically executed after the 6 hour wait time.