The classes (simplified):
The elves have jump boost and speed and can turn invisible in forests, but have the weakness effect other places.
The dwarfs have haste and night vision, but get blinded by sunlight.
The sea people can breathe under water, but are weak on land.
The demons can swim fast in lava, but water kills them.
The angels have an elytra, but they only have five hearts.
Plugins installed on server: ElementCraft, essentialsX