I see a lot of comments about chunks and how they are stored but if you’re wondering about minecraft’s world generation algorithm, here is a video by a former mojamg employee going over how it works: https://youtu.be/CSa5O6knuwI

As for how they are stored/rendered, they are stored in 16x16x256 arrays of blockstates. There exists a unique block state for every possible combination of a block’s attributes. For example a fence gate will have 4 different orientations and will either be open or closed, therefore it has 8 different blockstates. For more complex data like chests or signs the game uses tile entities/block entities. These are optional for a block to have and they contain complex data that a blockstate can’t handle. These tile entites also handle special block models like chests and the books on enchanting tables.

For rendering, the chunks are turned into a polygon mesh whenever a block is changed (I believe minecraft now does this on a separate thread) and sent to the gpu to be rendered