One issue in monetary theory is to determine endogenously which objects play the role of medium of exchange (e.g. Kiyotaki and Wright 1989). In order to focus on other questions, however, other...
Firms need money or capital to operate, to pay employess, to buy raw-materials and to earn profit
because money is just a medium of exchange used to make the buying and selling of goods and services easier.
money market is a market buying and selling of shares and security.
money is capital