Graphs that are connected vs strongly connected vs reachable
Connected: Usually associated with undirected graphs (two way edges): There is a path between every two nodes.

Strongly connected: Usually associated with directed graphs (one way edges): There is a route between every two nodes (route ~ path in each direction between each pair of vertices).

Reachable (from $A$ to $B$): A path exists in the graph between nodes $A$ and $B$. (Ability to get from one vertex to another)

Note: Got some terminology from:
https://mathoverflow.net/questions/6833/difference-between-connected-vs-strongly-connected-vs-complete-graphs