There are two kinds of roundabouts – the old-fashioned rondpoint, on which priorité à droite prevails, and carrefour giratoire.
The former means cars on the roundabout give way to ones coming on. The latter, which is now more common, is shown by road markings on approaching roads and by signage (usually a red triangle sign with circling arrows inside) indicating that the approaching driver should give way.
Initially less common, when they were introduced in the 1980s these were sometimes called rond-points anglais. Now most large roundabouts are giratoires, Paris’s Place de l’Etoile being a famous exception.
French rules for which lanes to use also differ from the UK’s. The guidance is that you use the right-hand one if going right or straight on and the middle one if leaving further round than that.