Here's a picture: 
Actually, it'd be helpful to know what they all meant.
What does the skull icon with the red waves on the Sauron’s Arthe screen mean
middle-earth-shadow-of-mordor
Related Solutions
Do they look like this?
If I'm not mistaken, those things are runes.
Whenever you kill a nemesis, there is a chance that they drop a rune. You can upgrade your weapons with these runes.
Since getting all the upgrades doubles your starting health, and they're all 20 and there's five of them, you start with 100 health points.
Best Answer
This icon indicates your currently selected target. If found and scanned, this target will appear on the HUD with this icon, and if you know where the target is through intel, their approximate position will be displayed on the map.