How do B-Trees work? Main Ideas
Each node of a B-Tree is an Index Record. Each of these records has the same maximum number of key-reference pairs called the order of the B-Tree. The records also have a minimum number of key-reference pairs, typically, half the order.
When inserting a new key into an index record that is not full, we simply need to update that record and possibly go up the tree recursively.
When inserting a new key into an index record that is full, this record is split into two, each with half of the keys. The largest key of the split record is promoted which may cause a new recursive split.