Espionage is when an assassin decides to get rid of an enemy they don’t like. A screen will show, showing which of the characters shown to assassinate. In a second example, they can also sabotage settlements, and damage buildings. The next log will be about spying.
The first infdev screenshot is from turn 146, where a Ebrum Assassin is trying to assassinate a Jester family member. In the second screenshot, during turn 162, a Paintarian assassin has a chance to sabotage a Floralian building.