A binary tree stores elements in nodes, with each node pointing to at most two child nodes. A binary search tree orders smaller elements to the left and larger elements to the right. section 7.2.1
The C++ map uses a binary search tree to store key-value pairs. The key determines whether each pair moves left or right, making searches faster than scanning every element in a vector. section 7.2.1
Following a search
Insert {1:a}, {3:c}, and {5:e}. The tree is reorganized so {3:c} becomes the top node, with {1:a} on the left and {5:e} on the right. Searching for {2:b} compares against 3, moves left to 1, and stops at that leaf. section 7.2.1
Figure 7.2 Three elements in a balanced binary search tree: nodes with smaller keys go on the left and larger keys on the right.
Use the balanced-tree figure to see how key ordering places smaller nodes left and larger nodes right. section 7.2.1



