It can mean several things, depending on the context. It comes from the verb 'draw' meaning to pull A draught can be a current of cold air. For example, if a door doesn't fit well, draughts of cold air get drawn into the room. If you sit near a draught, you feel cold. A 'draught' beer is a beer that is pulled under pressure straight from the barrel, as opposed to a bottled beer. NB American English spells this word the same as 'draft', as in the first copy of a document or text. British spelling makes a distinction between these words.

Don't forget the popular board game of draughts (https://en.wikipedia.org/wiki/Draughts). A "draughtsman" makes technical drawings. (http://www.oxforddictionaries.com/definition/english/draughtsman)

... or in other words, there's a issue of meaning here, as opposed to just spelling.

Only in some cases! 'Draft' as a verb, or 'draft' in the sense of 'a draft copy', is spelt with an 'f' in British English. British English makes a spelling distinction between the different meanings of the word, whereas American English doesn't. If you 'translated' all instances of American uses of 'draft' into 'draught', some of them would be wrong.

It's the British spelling of the word that in America and Canada is spelled "draft."