Broadly speaking, an arthouse movie is one where entertainment value isn't prioritized, and such movies are typically more serious, strange, and perhaps less approachable, too. That's not to say arthouse movies are intentionally boring or pretentious (maybe some are, but it's subjective), yet they can be potentially slow or obscure in parts. A great many arthouse films can be broadly described as dramas, but an arthouse movie can fall into any genre, really, so long as it retains the feeling of being artistic, ambitious, and distinctive.