Explore the procedurally-generated landscapes, towns, dungeons, forests, and cave systems.
Stop to admire the butterflies or to stare at the weird egg things in the water. The world is alive with flora, fauna, and flauna.
Use various tools to mine and collect resources for trading or crafting. The whole world is destructible.
Use fire to your advantage. Or accidentally destroy your limited sources of timber. (Keep a bucket handy.)
Keep your friends close and your frenemies closer. Use axes, swords, crossbows, hammers, and magic to make new friends.
Build a house and live there, forever. Wear a cape indoors if you like. (protip: Don't live next to lava.)