One of the eight parts of speech, adjectives are a type of modifier; that is, they modify or describe nouns in a certain way, letting you know the size, shape, weight, color, nationality, or any of a myriad other possible qualities of nouns.
The Italian definite article (il, lo, la, i, gli, le) indicates either a particular noun or, contrarily, the general sense of a noun.
Demonstrative adjectives (this, that) are used to indicate a specific noun or nouns. In Italian, they must agree with the noun(s) in number and sometimes gender: questo, quella, quei ….
The aptly named indefinite article (un, uno, una, dei, degli, delle) indicates an unspecific or unidentified noun.
One of the eight parts of speech, a noun is commonly defined as "a person, place, or thing." If that seems vague, that’s because it is.
The partitive article (del, dello, della, dei, degli, delle) refers to an unspecified quantity of food, liquid, or some other uncountable noun. English has no equivalent article – the partitive is usually translated by the adjectives “some” or “any,” or may be left out entirely.