graph vs DAG vs tree

gistfile1.txt

A Tree is just a restricted form of a Graph.

Trees have direction (parent / child relationships) and don't contain cycles.
It has only one path between any two vertices

They fit with in the category of Directed Acyclic Graphs (or a DAG).
So Trees are DAGs with the restriction that a child can only have one parent.

Directed Acyclic Graphs is a kind of directed graph that have no cycles.

DFS will create a spanning tree of a graph. So does flooding.

control-flow graph --> DFS --> spanning tree --> tree travesal (pre-order, post-order, in-order)
CFG may contains loops, nodes with multiple incoming path.

topological ordering/sorting is a concept for directed graph which has no directed cycles, that is, DAG.
Travesal method is for graph. This includes tree as it is a rectricted form of graph.
RPO (Reverse Post Order) of a DAG has another name: topological sort.

tree edge
back edge
forward edge
cross edge

https://eli.thegreenplace.net/2015/directed-graph-traversal-orderings-and-applications-to-data-flow-analysis/