Bukkit

What exactly happens, when limit of 'spawn-limiter' will be reached?? Some RANDOM mobs will be despawn and new mobs spawn, or mob spawning just stop ??

And what exactly you mean under 'mobs' and 'animals' ??

1. Mobs = all enemy monsters (zombie, spider, guardian)
2. Animals = villagers, pigs, wolves, water squid ??

spawn-limiter puts a global limit on spawns. If the limit is reached, no more mobs will be able to spawn until some entities die or despawn. It's also checked on an interval rather then in real time to reduce resource usage.

Mobs = Aggressive entities such as zombies Animals = Non-aggressive entities such as a villager