Three lines, no punctuation, no capital letters, and almost no scenery: the poem gives us only a sound and what that sound sets off. Rain is falling, and its noise becomes a "sweet song." Out of that song "springs" laughter, and the last line draws the lesson: "simple beauty is." The central idea is that beauty doesn't need grandeur or effort. It can be found in something as ordinary as weather, if we are willing to listen to it as music.
The shape of the poem backs this up. Counted out, the lines run five, seven and five syllables, the same pattern as the traditional haiku. Within so small a frame, every word has to earn its place. There is no rhyme. Instead the poem relies on sound. The soft *s* sound turns up in "sweet," "song," "springs" and "simple," and it hisses through the poem much as rain hisses on leaves or windows. The middle line, the longest at seven syllables, also does something. "Springs out delightful laughter" is the line that overflows, and the extra length makes it feel as if the laughter really is spilling over the edges of the little poem.
The imagery is unusual because it is nearly all sound. We aren't told what the sky looks like or where the rain falls. "Sweet song" borrows a word from taste to describe something heard, which softens the rain at once. This is not a storm or a downpour but something gentle, even pleasant. The poet has chosen to hear the rain as a song rather than as noise, and that choice is the poem's real subject.
The verb "springs" is worth slowing down for. It suggests something leaping up suddenly, but it also brings to mind a spring of water, which fits a poem about rain. The season of spring may be faintly present too, though that is an inference rather than something the poem states. The grammar is also slightly unexpected. The song "springs out" laughter, as though laughter were something the rain produces, like water from the ground. The poem never says whose laughter it is. It could be the listener's, or children's, or the rain's own, and leaving it open lets the laughter belong to everyone and everything in the scene. One could even imagine that the patter of drops sounds like giggling, though the poem doesn't say so.
"Delightful" is the most openly emotional word here, and it is a little more formal than "happy" or "funny." It also has "light" hidden inside it, a small brightness tucked into a poem about rain. Meanwhile the vocabulary around it is deliberately plain. The whole first line is made of one-syllable words, and the rest of the poem rarely goes beyond two syllables, apart from "delightful" and "laughter." The language is as simple as the beauty it describes, so the poem does what it says.
The ending is the most interesting part. "Simple beauty is" stops on a verb that has nothing after it. We can read "is" as meaning "exists," a flat, confident statement, like saying "love is" or "the world is." Or we can feel the sentence waiting to be completed, with the reader invited to supply what beauty is, perhaps by pointing back at the rain and the laughter. Because there is no full stop, the thought never quite closes. The title, three asterisks in place of a name, adds to this effect. The poem begins as if we had walked in on something already happening, so the first line has to serve as its title.
Look at the order of the lines and you will see a movement from the concrete to the abstract. First comes rain, something we can hear. Then comes laughter, a human reaction. Finally comes "simple beauty," an idea. Nature leads to feeling, and feeling leads to understanding, all in about a dozen words.
That is the poem's significance. It makes a small argument without arguing, and it trusts the reader to notice what is easy to miss. For a student, it shows how much a poem can do through arrangement, sound and restraint. It also asks a question about our own habits: how many times have we heard rain as a nuisance, when it could just as well have been a song?