Regarding ARTICLES, Swan stablishes that

Articles are small words that are often used at the beginning of verb-noun phrases.

Articles can show whether we are talking about things or actions that are known both to the speaker/writer and to the listener/reader.

The correct use of the articles is one of the easiest points in English grammar. Fortunately, most article mistakes do not matter too much.

Most languages of Western European origin, and one or two others, have article systems quite like English. However, there are some differences in the way articles are used in English and these other languages.