Within Rogue Survivor, events are incidents that bring enemies and items into the current map.
Events which have a positive effect on your gameplay, assist you and usually other survivors, and help you achieve your goals.
Military Supply Drop - While not as filling as three tins of food which you could fit in the same slot, rations are proberly the most reliable source of food later into the game, and with the addition of medical kits, supply drops are very helpful and sometimes even life saving events.
National Guard Deployment - Every once in a while, the National Guard is deployed nearby. While they may use your supplies, with dozens of well trained men running about, zombies are going to have a hard time getting to you, without being shot at by a dozen guards.
Roguedjack Visits- Rarely, you will get the message "You hear someone speaking French" and an 8-bit jingle of the French national anthem will play. This signals the arrival of Roguedjack (the creator of this game) on your block. He has 3 hauler, 5 hardy, 5 leadership, 5 charismatic, and will proceed to beat zombies to submission with his unique keyboard weapon. He also carries an extravagent amount of food with him. The game will definitly get easier with him and his entourage running around, but they might steal your supplies.
Things which will have both or a positive or a negative outcome, or do not affect you.
New Refugees - Additional civilians may help reduce the undead population or bring useful items to trade; on the other hand, they might just steal your supplies or become zombified.
Gangsters - While they will steal your things, either by killing you or by breaking into your safehouse while you're out, they do bring in a good source of amunition and weaponry. As long as you don't have to kill them yourself, they can be a good source of items, and somewhat reliable.
Events that will usually have a negative impact on your game.
Black Ops - These NPCs will rush through the street, quickly eliminating anything which moves, other then other black ops. While they supply very good weaponry, the risk is too dangerous to attempt to kill them for it, and not many people or zombies can manage to kill them. Their range of weaponry is another problem - shotgunners are easily killed by black op snipers, while snipers and people will long ranged weapons will quickly be ambushed around corners by them.
Bikers - While not very dangerous, these people do not have any decent firearms or supplies, and thus, all they do is take items you might want and make you spend your ammo on them. Thus, while not harming you if you have the sense to use a good firearm, they will waste your bullets and your food.