The poem Fireflies in the Garden, by Robert Frost is an allegory to several things including the admiration of effort, the drawbacks of imitation, and the appreciation of differences.
The setting of the poem is a garden during dusk, and when the twilight begins to let things shine in their own light. Two things are shining: In the sky, there are the stars coming out, and in the garden there are the little fireflies.
The poem goes:
Here come real stars to fill the upper skies,
And here on earth come emulating flies,
That though they never equal stars in size,
(And they were never really stars at heart)
Achieve at times a very star-like start.
Only, of course, they can't sustain the part.
Basically, Frost is admiring the fireflies for trying to shine like the stars since we (as people) should always shoot for the stars and imitate the good and intelligent behaviors of peers.
Yet, he also warns us not to try to become replicas of something else, just like the fireflies can only shine so much and last so long. They could never become stars, but yet, they can shine like one in their own time, and at their own pace.
It is a very simple poem, but the simplicity is what provokes in the reader the most appreciation for the central message of the story, which is to simply shine, and continue shining for as long as you are able to shine.