I think this poem is about a guy stopping in the woods while it is snowing one evening.
He is in the woods and is going to stop.No one is around.His horse is confused why they are stopping without a farmhouse.The horse shakes his bells, the only other sound are the easy wind and downy flake.He admires the woods but then remembers he must keep going.
The woods are filling with snow. The horse is shaking his bells. downy flake. Dark, deep woods.
The speakers tone is serious and relaxed.
The speaker says "but" to shift the attitude of the poem.
The theme of the poem is that people must consentrate on flfilling promises/ duties without being distracted.