There is a very fine line between sales and marketing, so much so that there really is no point sometimes trying to split them up!
Both sales and marketing are there to try and persuade someone to buy, both cost money (expenditure - someone gets paid to sell, right?) and both make money (sales). Both deal with psychology... but I guess if I was to define it more, marketing helps create the problem/ reason for the sales/ advertises the product, and sales solve the problem/ deals with the leads that come in. But honestly, it's all the same!
Hence why everyone's answers here are all right as well.