An article is a type of adjective or pre-qualifier. Adjectives give more information about nouns.
An article is also known as a pointer or determiner and comes in two
main forms: a/an is the indefinite article (any old thing) and the, which
is the definite article (a specific thing): a table (any one), an organiser (any one), the book (the specific one in your hand).
Note that a/an can only be used before singular nouns: an organiser becomes the organisers (the ones who have arranged the conference) or just organisers (any mass of organisers) in the plural.
Articles are usually found before concrete nouns but may not be found before abstract nouns.
Check in the Mech Concordance for common usage of the word or phrase you are wishing to use.