Why this one needs a probe
MTR needs the same raw sockets as ping and traceroute, so it cannot run in a browser. A real probe runs it and returns the report unedited.
When you’d reach for this
When a connection is intermittently bad rather than plainly broken. A single traceroute is one snapshot; MTR keeps measuring, so a hop dropping a few percent of packets stops hiding.
Learn the idea behind the tool
This tool is the fast answer; the lesson is the understanding. Start with How routing decisions work.