Feature articles are exactly that, a 'feature'. It may be informative or merely entertaining (infotainment). Most feature articles are about a place, an expression (eg. words), perhaps an experience.
They are usually informal, although they rarely use colloquial language (slang). The language techniques are used to build repartee with the audience (ie for the audience to sympathise or to relate) and they include word choice, sentence structure (short sentences, single word sentences etc), pull out quotes, headings, subheadings, pictures, anecdotes, rhetorical questions etc.
A feature article is NOT an essay.