Consider the Binary Tree:
Pre-order traversal(root) is traversing the node then left sub-tree of the node and then the right sub-tree of the node.
So the pre-order traversal of above tree will be:
1 2 4 5 3 6 7
In-order traversal(root) is traversing the left sub-tree of the node then the node and then right sub-tree of the node.
So the in-order traversal of above tree will be:
4 2 5 1 6 3 7
Post-order traversal(root) is traversing the left sub-tree of the node then the right sub-tree and then the node.
So the post-order traversal of above tree will be:
4 5 2 6 7 3 1