Historically, the prefix "a-" derives from a preposition that was used before the gerund form of a verb. Johan Elsness cites an example of this in his paper On the progression of the progressive in early Modern English from Old English:
... yrstandæ ic wæs on huntune ... . (From Ælfric, Colloquy 68) 
In the above quote, "huntune" is ...
Such introductions and descriptions are called epic catalogues. Barbarians are sometimes known to refer to them as epic catalogs.
The term catalogue is not restricted to characters. Lists of armies, ships, places, etc. are also covered by the term. As far as I am aware, there is no specific term for any of these; they are all just called catalogues and ...
This is not a direct answer to the question in the sense of a general term, but there is a very well-known term for a specific example: the teichoskopia in Book III of the Iliad, where Helen stands atop the wall and catalogues the Greek chieftans.
Depending on the context and your audience, you may be able to use "teichoskopia" as a general term, ...
These are very rare in English (I don't know how common they are in Spanish); I've identified two poems that have them. A word fr them is headnotes.
Some of these are arguments. From Wikipedia
An argument in literature is a brief summary, often in prose, of a poem or section of a poem or other work. It is often appended to the beginning of each chapter, ...
Thinking about this poem and the emphasis on the dogs being in the 'very middle' of the path, I picture the coupled dogs not like this
or even like this
but like this
In this situation the dogs can't separate until everything 'subsides' and can get hurt if they try to pull apart:
(this is a more detailed explanation from LovetoKnow.com, spoilered just in ...
Most of this is answered by the poem itself.
We have the repeated line:
You will tell them, my country,
which implies that "you" is a country, clearly Mauritania.
We have the lines:
You will say to them, to your people,
you will say to them, the encampments,
you will tell them, her people,
which mean that "they" are the people of ...
With so little to go on, it is difficult to be certain. It is possible that the person in question was a Consul General at Large of the United States.
The published poem gives his location as Washington DC. which makes the diplomatic George H Murphy the more likely candidate of those individuals thrown up by internet searches.
This reference to him in a List ...
If you look at Google books, it finds several instances of this rhyme labeled 1917, 1918, and 1919, and a few from earlier years. Looking at these more carefully, the earlier hits are all mislabeled, and the hits labeled 1917 are in bound volumes of periodicals that extend over several years, so they actually appeared in 1918 or later. Here is the earliest ...