Peace is a mechanic in Hexagor.io. It is used so that two Empire's may not attack each other in any way. Making peace with someone can be very useful, and is best used making peace with all opposing large Empires near the player's Capital, so that there is a barrier to protect you from other Empires, as well as those ones. Currently, each empire can only make peace with two empires.
To make peace with another player, go to the Alliances Menu at the top-right, and click send request, then click on any other Empire's territory. Both Empires must agree to make peace for a peace treaty to work. When receiving a peace request, you can select the check mark at the top-right of the game.
It is important to avoid being surrounded by peaceful expires, because once a peace treaty is agreed on, it can never be revoked without either empire leaving the game. As long as a tile is claimed by a peaceful empire, you can never get through it, not even with conquests or breaking tents. Therefore, one should make sure there is a way out before making peace with large empires, and do not assume that peacemakers do not have malicious intentions. Usually, making peace with two empires on the same side of your capital has a lower chance of being surrounded by them.