Yet another American/British linguistic difference. In North America, a catbox is, it appears, the shallow plastic tray (sometimes furnished with a cover) in which you put cat litter for your cat to crap on in a reasonably sanitary fashion, assuming that you don't do the sensible thing and encourage the beast to go and shit in your neighbours' flower beds instead. However, in the variants of English spoken in places where a bathroom is a room with a bath in it, that object is, marginally less euphemistically, known as a litter tray, while a catbox or cat box would be the more or less secure ventilated container in which you attempt to put your cat, following much searching and/or extraction from underneath furniture (since the little bugger will certainly have determined your evil intent well in advance, and skedaddled) to transport the said animal to the vet/cattery.