Does pirate, buccaneer and privateer means the same?

Not exactly. Pirates, sailing on the ships or boats, attacked other ships or coasts. Buccaneers have also been pirates, but they served the ruler, who wanted to harm the opponent fleet without spending any money. The ruler allowed buccaneers to rob or kill with no punishment and keep part of the loot. A privateer was a member of a crew on an armed trading ship waging a sea war; that also came to gathering goods pulled from the enemies.