In Minecraft, everything spawns in chunks, a 16 x 16 block space that is 384 blocks tall. Chunks load one by one and can be adjusted by the render distance.
Every time a player travels 64 blocks, they enter a new chunk. There are borders separating each chunk from the next.
However, these borders aren't always visible. In fact, it's pretty difficult to tell where one chunk ends and another begins unless it hasn't been loaded. Players can go in and out of a chunk without ever realizing it.
Fortunately, chunk borders can be visible in Java Edition. This doesn't happen ordinarily, but players can certainly turn them on.
It is really easy to make chunk borders visible in Minecraft Java Edition
Chunk borders can be viewed easily in Java Edition, thanks to an incredibly simple method.
Java Edition is a much more optimized version of Minecraft, which is evident in many of its unique controls. All players need to do to view chunk borders is press two keys on their keyboard: F3 and G.
Once that is done, a message may pop up on the screen indicating that the chunk borders are being shown. The same keys can be used to turn them off and back on. This can be done over and over again.
In Bedrock, there is no way to enable chunk borders, and they cannot be seen on the screen. There is, however, a way to tell whether players are at a chunk border or not.
Before using this method, players must have coordinates turned on. This can be done in the world settings before or after the creation of a world. It won't have any effect on achievements or anything like that.
Once this is done, players should return to the game screen. There should be a set of three coordinates in the top-left corner of the screen. These will change as players move around.
The three coordinates are x, y, and z (in that order). If an x or z coordinate is divisible by 16, players are at the edge of a chunk border. If both the x and z coordinates are divisible by 16, that is the northwest corner of the chunk. For example, if players are at (321, 56, 1600), it means they are at the end of a chunk. Meanwhile, if they are at (48, 77, 80), they are in the northwest corner of that chunk.
Why would Minecraft players need to know chunk borders?
Chunk borders are important for building and other things in Minecraft. They're an inherent form of measurement in the game, which can make building things and lining them up properly easier.
The best use for them is arguably when players die and lose their loot. Once players enter the chunk the loot is in, they have five minutes before it despawns and is lost forever.
This can often lead to players frantically searching and not finding their stuff in time. If they have a plan before entering the chunk, it makes the loot much easier to find.