the structure of the main end island, mineshafts, nether fortresses & the ocean monument has changed
there are some new mechanics
added mobs
a new trash slot
2 new dimensions, the undergarden & the bumblezone
the behaviour of spiders has changed, they can now climb any surface
there is now underground earth quakes
added bosses
new ores, weapons & armour
a hidden cave biome filled with dinosaurs and other creatures as well as other biomes
over 100 biomes added to the overworld
new nether & end biomes
a deep ocean hidden beneath the arctic
large monsters appear in the ocean during a storm
a horrifying dweller lurking around in the caves
you can also craft a backpack
the nether has been amplified
and a few visual changes