An Allusion is an indirect reference to any person, place, or thing factious, historical are actual. Sometimes, to understand an allusion in a poem, we have to find out something we did not know before. But usually the poet asks of us common knowledge.
Allusions not only you which the meaning of a poem they also save space. In "The love Song of J Alfred Prufrock, T.S. Eliot, by giving a brief introductory quotation from the speech of a damned soul in Dante's "Inferno" is able to suggest that his poem will be the confession of a soul in terment who sees no chance of escape.
