Trailing edges in a graph

Question

I hardly understand the Tarjan algorithm for articulation points. I am currently following this guide: https://www.hackerearth.com/practice/algorithms/graphs/articulation-points-and-bridges/tutorial/ . What I really don’t see and don’t see in any other textbook is what the “back edge” means. Given the graph presented there, I know that 3-1 and 4-2 are trailing edges, but are also 2-1, 3-2 and 4-3 trailing edges? Thank.

Answer 1

... a Back Edge - , , .

.

: DFS , - , . : 0->1->2->3->4. , 4-2 3-1. DFS 3, 1, 1 , back edge , , , .

: 2-1, 3-2 4-3? . , DFS 0->1->3->2->4, 2-1 4-3 - .

Answer 2

:

DFS , Back Edge - , , .

2-1, 3-2, 4-3 "Back edge", DFS.

Answer 3

, DFS, A, B C, AB, BC, , node C, CA, , . , A-B B-C , C-A , node.