The poem begins by shrugging off purpose. The speaker says you aren't really chasing a white moth through the forest; it just happens to be flying ahead of you. Things come to you when you walk, and you come to them. It's a relaxed way of describing attention: you don't hunt for meaning, you drift into it.
The second part settles on a small woodland pool, fed by spring rain, where water lingers because it "doesn't quite know where to go." The speaker is clearly delighted, watching ripples spread, cross, and cancel one another, and sees in them a picture of how any point can be the center of its own universe.
Then the mood shifts. The closing three lines bring in "song dogs," a name often used for coyotes, hunting "some ripe panic." After the calm of the pool, the ending feels sharper and wilder, as if the forest holds both quiet wonder and predatory urgency side by side.