Who is “Childe Roland” and what does he do at the Dark Tower?

In Robert Browning’s poem, “Childe Roland to the Dark Tower Came” (1855), Childe Roland is a knight errant in search of the Dark Tower.

When he reaches it he blows his horn, the poem ends.

The title comes from a piece of a song in Shakespeare’s King Lear (act 3, scene 4).