In this world that you don't know about
It seems like the new mobs that you never have seen before
new ores and new stuff that never seen before
you had noticed that there a new gui called Just Enough Items (JEI)
you can also click on your F7 key the light levels. Yellow x means mobs could spawn. Red x means mobs can spawn anytime.
Look like new tools that you can craft and new ores to mine up. Noticed some of the new ores have a mining level
New furnaces that make smelting go faster than regular furnaces. Leafs decay faster than normal. The chest can now have updates to them.
Wait you can carry items into backpacks. New Shields & New ways to build real-life items and real-life foods
New Blocks that have new guis and can hold coal or lava to make power. new ways to the storage your items into a new system

