There are 8 different NPC stations. They are:
There are 5 conversation types:
Each combination of NPC stations and conversation type (ie. Soldier Gossip or Noble Interview) corresponds to a "lever". Levers are just counters that exist within each city where you do civic diplomacy. Winning a civic parley will increase the associated lever by 1 (more as you get to higher presence levels).
When a particular lever reaches 40, everyone in the city/town will immediately get the buff associated with that lever. As long as the lever stays above the threshold value of 40, everyone entering the city/town will get the buff as well. Once the lever goes below 40, or the player leaves the city/town, the buff will begin counting down. All buffs have a 1 hour duration (at least the ones I have seen...could be different in the future).
Levers decay over time, losing (or gaining) 1 point every few minutes. Normally the levers will begin at 10. If you raise a lever to 40 and then stop doing that particular parley option, the lever will eventually decay back to 10. Many levers oppose each other. For example, Soldier Incites will oppose Soldier Convinces, Entertains and Interviews. Every time you raise Soldier Incite by 1, you will also lower the other 3 Soldier parleys by 1. Levers always oppose each other within the same station. The exception is Gossip parleys. Gossip never opposes, or is opposed by, any other levers.
If you lower any levers below 10 via raising an opposing lever, that lever will "decay" back toward 10 (it will increase by 1 every few minutes until it reaches 10).
For a more complete explanation of how civic diplomacy works, refer to: