Money is cash. You can have money in your pocket or money in the bank. People need money to buy things.
Every country has an agreed upon type of money: in the United States, it's dollars and cents. People need money to buy food, furniture, clothes, books — everything. You can't buy stuff without money. People may also invest their money in stocks and property. Using a credit card is a way to buy things when you don't have any money on you — so is a check. Most people want more money, and people will do a lot of things to get it.