Old English (or, Anglo Saxon) prosody, that is, the way verse is composed (especially, the way the verse sounds or the lines rhyme) is characterized by, among other things, caesura, alliteration, assonance, and kenning. It is almost impossible to read ten lines of any Old English poem, from Beowulf to Deor's Lament, without encountering all or most of these techniques.
The Seafarer, most likely from the 9th or 10thC, a lyric about a seafarer who is both beaten up by and drawn to the sea, is relies heavily on the elements of prosody above. All Old English poetic lines are broken into two half-lines called hemistitches, with a pause between the lines, called a caesura:
Maeg ic be me sylfum sothgied wrecan,
sithas secgan, hu ic gewschwindagum (ll.1ab-2ab)
I am able to make a true song about me myself
to talk about my travels how I often suffered (endured)
As you'll notice, I labeled the two parts of the first full line as 1a and 1b, a very common way of designating the two hemistitches for easy reference. As the first educator indicated, we believe that, because Old English poetry was, first, oral, the caesura provides a natural stop for the poet (the scop) to breathe, and it may also help the scop to memorize lines. Another theory argues that the pause helps the audience to recall key lines more precisely.
You will also notice that the third hemistitch (2a, sithas secgan) is an example of alliteration, the repetition of initial consonant sounds. The first syllable of each word (sith and sec) is stressed and therefore carries the important part of the message for those two words. There has long been a theory that Anglo-Saxon scops used such stressed words to keep the attention of their hard-drinking, not-so-alert audiences.
Another very common poetic technique is the use of kennings, loosely defined as a compound word, often a whole phrase, that refers to people or things by naming a quality that the person or thing exhibits. For example, the seafarer creates a great image of what it is like to suffer on the cold sea when he says,
northan sniwde, hrim hrusan bond,
haegl feol on eorthan corna caldest. (ll.31ab-33ab)
It snowed from the north frost covering the ground (sea),
Hail fell on the earth coldest of grains.
The kenning corna caldest (coldest of grains) allows the scop to create a concrete image of intense suffering for an audience that might not, at this point, know much about suffering on the cold ocean in an open boat. By this time, let's say the 10thC., the great expansion of Anglo Saxons was largely over, and many in that culture were farmers rather than sailors, so the scop takes the experience of the open-boat voyager and puts it in terms an agricultural people could understand, one of the most common and important uses of the kenning. In addition, the phrase haegl feol is an example of assonance in that the letters ae in haegl and eo in feol are pronounced like an ay in the modern English word say.
Each of these techniques is an important part of the Old English oral tradition and designed to make memorizing hundreds of lines easier for the poet and for the audience.
"The Seafarer" is an Anglo-Saxon elegiac poem. As with many Anglo-Saxon texts, the poem contains caesuras, kennings, assonance, and alliteration.
Caesura is a sound break in the middle of a line. This allows for the scop (the one responsible for passing on the oral tradition of the tale/poem) to take a breath and pause for dramatic effect. An example of caesura is found in the following line: "hung with icicles; hail flew in showers." The semicolon acts as a reminder to pause.
A kenning is a metaphor which is used to elevate and beautify the language. For example, "sea-paths (in line 29) is the ocean.
Assonance is the repetition of a vowel sound within a line of poetry. Line 12 contains assonance: "the sea-weary soul." Here, the "e" sound in sea and weary repeat.
Alliteration, on the other hand, is the repetition of a consonant sound within a line of poetry. Line three contains alliteration: "tell my travels." The repetition of the "t" sound depicts alliteration.