This is probably the most important of all of money's attributes. Money needs to be accepted by all members of a society as a valid form of exchange. Technically, anything can be used as money: If somebody wants a product or a service they could offer another product or service in return for it, but this is a barter system and not accepted by all members of the society.
Money must be able to withstand the wear and tear of being passed through so many different hands without falling to pieces or disintegrating. Nowadays, money is in the shape of very durable paper, coins and as an electronic medium, which is completely safe from harm.
This means that all money with the same face value in a particular society has the same face value, and also the same monetary value. This may seem obvious: Of course all ten dollar bills are worth ten dollars, but in the days when people relied on gold and silver coins there could very often be different amounts of precious metals in the coin, so two coins may have looked alike, but were worth different amounts.
Money has to be able to be divided into smaller units so that the real value of a product or service can be given. For example, if you wanted an apple but the only money available were hundred dollar bills, it would be a pretty expensive apple.
Money has to be easy to carry otherwise it would be far too cumbersome and difficult to manage. The barter system may be good in some circumstances but on a day to day basis it is far too inconvenient.