Beowulf is an epic poem from the Anglo-Saxon period. Not only is the poem an epic one, it is also a heroic poem (which tells of the achievements of an epic hero). Texts such as this use elevated language (formal language) and elaborate literary devices (such as kennings and alliteration). A kenning is a two word, typically hyphenated, to describe a word in a more beautiful and image-ridden way. Alliteration, on the other hand, is repetition of a consonant sound within a line of poetry. Alliteration adds to the flow of the line and gives it a musical quality (important because many poems from the period were sung).
Based upon the original form of the poem, it was sung, language needed to be filled with modifiers (words which illuminate the image readers picture when heard). Many modifiers modify a noun or a verb. These are called adjectives. For example, consider the following sentence:
The tall man hastily ran out the door.
The word "tall" modifies the noun man, and the word "hastily" modifies the verb ran. Without these words, the grammatical correctness of the sentence would not change, but readers would be left with less information about the man and how he ran.
As for the epic of Beowulf, many modifiers are used. This elevates the language of the poem and offers readers more information about what is specifically going on.
For example, in the opening line of the text, it is stated that the Danes had achieved glory through "splendid achievements." The word splendid modifies achievement, stating what kind of achievement they had obtained. Therefore, this tells the readers that their glory was not due to simple achievements, but splendid ones.
Perhaps the most important modifiers are present when the tale defines Beowulf himself. Without the modifiers, Beowulf would not be seen as the true epic hero he is. Instead, he would be described in a very simplistic way.