The title. I've been trying to figure this out and how it works. please help.

Spreads your religion, the bigger number of believers the higher tier of religion tenants it unlocks. Some are pretty powerful.

MumbaUmba wrote:

Spreads your religion, the bigger number of believers the higher tier of religion tenants it unlocks. Some are pretty powerful.

That makes sense. Thanks.

Faith gives you bonuses via tenants.

Also you get grievances/claims to any territory with believers in them. That is you can get the AI to give them to you, and you also build up war desire so you can go and bash them over the head and seize a bunch of lands from the AI and a bunch of war points to get gold and land etc from the AI when they surrender.

But how to spread a religion? I can build a monument, and that's it, I don't see any other buildings related to this. 

For Lucy OpenDev, it should be mentioned that the MAX number of Holy Sites is 5.  (One initial and one for each tenet tier I'm guessing.) [If your empire sprawls across several continents it would mean believer on different continents would have to travel a lllooonnnggg way to visit a Holy Site.]

Kotli wrote:

Also you get grievances/claims to any territory with believers in them. That is you can get the AI to give them to you, and you also build up war desire so you can go and bash them over the head and seize a bunch of lands from the AI and a bunch of war points to get gold and land etc from the AI when they surrender.

This is not exactly the case you get grievance only if they have religion different to yours and their territory follow your religion. (And other way around). Technically they can switch to your religion and actually became religion leaders themselves,