Or titles can tell you what the poem means, if you don't get that from the poem itself. Titles can complete the poem. Here's an example I found in Richard Russo's "Bridge of Sighs," the novel I'm currently living in:
He rose up on his dying bed
and asked for fish.
His wife looked it up in her dream book
and played it.
Title that!
It's a poem by Langston Hughes. Its title is "Hope." Beats me why, but in the novel people think the title explains the poem.