It's a bit of both. The Conjuring movies are based on the real - life cases of Ed and Lorraine Warren. However, the movies are fictionalized for entertainment purposes. They take the basic elements of the Warrens' investigations and add a lot of Hollywood - style scares and drama.
Well, it's inspired by real-life cases but the movie adds a lot of fictional elements for entertainment purposes. The basic premise might have roots in reality, but it's not a 100% accurate account.