Difference between 'Run and gun' and 'Stop and pop'
While both tactics are valid in most FPS, certain game engines favor one over the other. Run and Gun suggests that your character never needs to stop, while stop and pop suggest the exact opposite, by having the need to stop before you shoot your opponents. Gameplay reasons why stop and pop is needed over run and gun; the game engine makes your aim drastically inaccurate when running, and your rate of running is quite slow.
What is Run 'N Gun?
Run 'N Gun is a popular concept that is a very luck-oriented strategy. Run 'n gun is usually used once the player has used a few strategies that didn't work and is tired and frustrated by the game. Run 'n gun's purpose usually is to just get through the level without getting killed, while escaping your enemies. Escape is the word used because, generally, you are focusing on surviving rather than killing all the enemies. Of course run 'n gun is also used when players want to rush an enemy. There really isn't a strategy involved it's just exactly what it says. You run in, guns blazing, hoping that you do some damage. While this tactic can be useful against unprepared enemies, the tactic can also become very bad if your enemy is ready for you. Another time Run 'n gun is used is during a stealth game when your cover has been blown. At this point, the enemies are all after you and you are just trying to stay alive, by firing that machine gun you've been so itching to use rather than your silenced pistol. So, the strategy Run 'N Gun has highly variable effects, depending on how prepared you and your enemy are.