1.  What is a tree? 

2.  What is the relationship between parent node and child nodes? 

3.  What are a key and a value? 

4.  What is a root node? 

5.  What is the purpose of a left child node and a right child node? 

6.  What is a leaf node? 

7.  What is the depth of a tree? 

8.  What is the size of a tree? 

9.  How do you calculate the size of a tree? 

10.  Can a tree have a duplicate key? 

Answers
1.  A tree is a data structure where data is stored in nodes. Nodes are arranged in branches where each node can expand into 0, 1, or 2 other nodes. 
2.  A parent node is a node that branches into one or two other nodes, which are called child nodes. 
3.  A key is a component of a node that identifies the node. An application searches keys to locate a desired node. A value is also a component of a node that is used to store data. 
4.  A root node is another term for a parent node. 
5.  The left child node has a key that is less than the key of its parent node. The right child node has a key that is greater than the key of its parent node. 
6.  A leaf node is the last node on a branch and does not have any child nodes. 
7.  The depth of a tree is the number of levels of a tree. 
8.  The size of a tree is the number of nodes on the tree. 
9.  You calculate the size of a tree by using the following formula:
If the depth is 5 levels, then the size is 32, as shown here:

10.  No, a tree cannot have a duplicate key. 