The Waste basket is a place to store unwanted files. Emptying the wastebasket deletes all files in it permanently, so make sure there is no important files in there by mistake.
You can also have the option to delete files instantly without moving it to the wastebasket first. To enable this, choose "Edit, Preferences" from the file manager window, then on the behavior tab select "Include a Delete command that bypasses Wastebasket". use this with care. It is like using a shredder to destroy a document.