The essence of the t parameter in b-tree?

Question

Data Structures

I can't figure out what parameter t is used in b-tree.

The root contains from 1 to 2t-1 keys. Any other node contains from t-1 to 2t-1 keys

Why in b-tree the minimum number of keys in a node is not 1, but t-1? Logically, after all, in any node there can be at least 1 key? Help me figure it out, I'm still new to data structures.

Answer 1

There is such a tree, bamboo is called - it has no more than one descendant from each node. Bamboo does not branch. Bamboo, in fact, can only be called a tree conditionally - so, the list.
And the tree you are talking about is specially designed to branch abundantly at t>2. Because if you let him keep one child at each node, then bamboo can come out. You don't need bamboo.
What is unclear here?