Friday the 13th: The Game is getting single player challenges in the future. Think of it kinda like the Hitman games, where players will play as Jason and will have to eliminate counselors in a more cinematic way than the multiplayer mode like usual. Within these challenges, there will be three additional challenges that players can complete which will give them a new emote with each unlock meaning there is a total of 30 new emotes that can be unlocked.
The no survivors skull simply means that everyone in the challenge needs to be eliminated. The XP score is a certain score that players need to reach. You can earn XP Points by using stalker points, executing skills, regular kills and more. The undetected skull means you need to eliminate everyone without being seen. A notification will pop up if this skull is no longer available.