**Tree Edge****: **It is an edge that is present in the tree obtained after performing DFS on the graph. All the Green edges are tree edges as shown in the below image.

**Back Edge****: **It is an edge **(u, v)** such that **v** is an ancestor of node **u** but not part of the DFS Traversal of the tree. Edge from **5** to **4** is a back edge. The presence of a back edge indicates a cycle in a directed graph.

Consider an undirected graph is given below, the DFS of the below graph is **3 1 2 4 6 5**. In the below diagram, if the DFS is applied to this graph, a tree is obtained which is connected using green edges.

**Tabular between the back Edge and tree Edge:**

S.N. |
Tree Edge |
Back Edge |

1 |
It connects the node to its descendants. | It connects the node to its ancestors. |

2 |
It is the path traversed during DFS. | It is the path not visited during DFS. |

3 |
They can form bridges. | They can never form bridges. |

4 |
If it is disconnected, the number of connected components may increase. | Even if it is disconnected, the number of connected components remains the same. |

5 |
It never creates a cycle. | It can create a cycle. |

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