Weekend is Saturday and Sunday. Vacation is usually used for people who have several days or weeks to relax from work Holiday is usually used when people have some rest because of special official occasions like Christmas, New Year etc

"weekend" = Saturday and Sunday "holiday" (UK) or "vacation" means a period of time away from work when you relax, often in another place, like on a beach in Thailand! "day off" is a day when you do not work, for example, "Sunday is my day off every week"