The poem's first line and title make it clear that the speaker here is a mother talking to her son. The opening word and caesura—"Well,"—then make it sound like this speech is coming mid-conversation, perhaps as a response to something the son has said; it feels as if the mother is saying, "Look here." In any case, it's obvious right away that the speaker wants her child to pay close attention to what she's about to tell him.
Knowing the poem's context helps clarify what's going on here: Langston Hughes was a leading figure of the Harlem Renaissance, an explosion of Black artistic output in New York in the 1920s. His work frequently focused on everyday Black experiences, and this poem is no different.
The mother here is giving her son advice about how to survive and thrive in a racist society, and she bases this advice on her own life. She uses an extended metaphor of a rough staircase to emphasize how hard she’s had to fight in order to be successful. That said, the poem doesn't explicitly mention race, which allows its message to be taken as a broader call for perseverance in the face of hardship as well.
Back to that metaphor. The mother begins, in line 2, by proclaiming: “Life for me ain’t been no crystal stair.” The line repeats at the end of the poem, in line 20, and thus serves as a kind of refrain: it frames the poem, offering critical context for understanding the speaker’s advice. The “crystal stair” symbolizes the privilege and power that white people enjoy in a racist society. Crystals are smooth, glamorous, and beautiful. The symbol thus suggests that white people can achieve their dreams without many obstacles: they climb easily toward their goals.
But the speaker hasn't had an easy climb, a point she emphasizes in the actual sounds of the line. The line is thick with consonant /l/, /f/, /r/, /n/, and /t/ sounds:
Life for me ain’t been no crystal stair
These are harsh and sharp sounds, making the line sounds as dangerous and difficult as the life that she describes.