Other forms: daises
A speaker stands on a dais, or a platform, when giving a presentation. If you were speaking at the Coffee Lovers of America's conference, you'd step onto the dais so the audience could see you over their enormous cups o' joe.
Dais comes to us from the Old French word deis, which was originally pronounced with only one syllable — more like days than the current day-us. If you take a course in a lecture hall, your professor will need to stand on the dais so everyone can see her better.