影片 (yǐngpiàn) is a formal noun for 'film, movie', used especially in writing, titles, and official contexts (e.g., 纪录片 'documentary film'). It's more formal than the everyday spoken word 电影 (diànyǐng), which you'd use in casual conversation. 片子 (piānzi) is even more colloquial and can also mean 'X-ray image'.