What is the difference between John Galliano Haute Couture and Pret-a-Porter?

Pret-a-Porter is ready to wear, off the rack, off the peg, off the shelf. You simply buy stuff "as it is"

Haute Couture is french for "high sewing" and is custom-made or made to order for a certain client. Very highly priced and of course available to not a lot of clients. For menswear, the term is bespoke, or semi-bespoke.