Chunk

A chunk is a record that points to one of the shards and defines a range of keys associated to that chunk. The range of keys is expressed using minimum and maximum values. It doesn't actually store those keys.
For example, shard A with a key range from zero to 1,000. Shard B with a key range from 1,000 to 2,000. Shard C from 200 to infinity. A chunk does not store each key, it just defines a range of keys associated to that chunk.

• > use config
• > db.chunks.find().pretty()