Allegory :  is a form of extended metaphor, in which objects, persons, and actions in a narrative, are equated with the meanings that lie outside the narrative itself. The underlying meaning has moral, social, religious, or political significance, and characters are often personifications of abstract ideas as charity, greed, or envy.

Thus an allegory is a story with two meanings, a literal meaning and a symbolic meaning.

Ex : "And now, I said, let me show in a figure how far our nature is enlightened or unenlightened: Behold! human beings living in an underground cave, which has a mouth open towards the light and reaching all along the cave; here they have been from their childhood, and have their legs and necks chained so that they cannot move, and can only see before them, being prevented by the chains from turning round their heads. '' 

                                                                                                                                                                                                        (Plato, from Book Seven of The Republic, "Allegory of the Cave")

Caesura : is a natural pause or break.

Ex :                   Hwæt. We-Gardena     in gear-dagum,

                            þeodcyninga,        þrym gefrunon,

                            hu ða æþelingas       ellen fremedon.

Kenning : is a magic poetic phrase, a figure of speech, substituted for the usual name of a person or thing.

Ex : Fýrisvalla fræ ( seeds of the Fyris Wolds )   -     hauka fjöll ( mountain of the hawk )  ( from Beawulf )

Sonnet : A poem of fourteen lines, -- two stanzas, called the octave, being of four verses each, and two stanzas, called the sestet, of three verses each, the rhymes being adjusted by a particular rule.

Ex : Shakespeare's Sonnet 18.        Shall i compare thee to a summer's day?

                                                        Thou art more lovely and more temperate:

                                                        Rough winds do shake the darling buds of may,

                                                        and summer's lease hath all too short a date:

Meter : is the rhythm of a poet. 

Ex :  Look at the Sonnet 18 above. ( Iambic pentameter )

Rhyme : is a repetition of similar sounds in two or more different words and is most often used in poetry and songs.

Ex :   So long as men can breathe or eyes can see,

         So long lives this and this gives life to thee.                  (a, a )