A persona, from the Latin for mask, is a character taken on by a poet to speak in a first-person poem. Anthony Thwaite's 'Monologue in the Valley of the Kings' uses the word 'I' but it refers, not to the poet, but to the Pharaoh, Thwaite's persona in this poem. Sometimes a persona may persist across several poems, such as Wendy Cope's alter ego Jason Strugnell.
Dramatic monologues, as they must create a character, necessarily create a persona; however, as a poem using a persona need not tell a reader anything about the situation of the speaker, the narrative, or the person that the poem is spoken to, a persona-poem need not be a dramatic monologue.
Some critics prefer to treat every 'I' as a persona. The biographical truth (or not) of, say, George Szirtes' 'Preston North End', would be considered irrelevant. Others allow a belief in poetry as personal testimony, which Samuel Menashe insists on in his introduction to 'Self-Employed'.