Binary search tree: 1 value and 2 subtrees per node.
M-way search tree: M - 1 values and M subtrees per node. M is the degree of the tree.
In fact, each may contain up to M - 1 values. A node with k values must have k + 1 subtrees.
In a node, values are stored in ascending order:
V1 < V2 < ... < Vk
The subtrees are placed between adjacent values: each value has a left and right subtree.
V(i)'s right subtree = V(i+1)'s left subtree.
All the values in V(i)'s left subtree are < V(i).
All the values in V(i)'s right subtree are > V(i).