So one of the most important topics in finance is time value of money. Everybody knows that the value of money in the future is less. Example, if you have $1000 today and if you keep it for 10 years, it will buy you LESS things in the future. This is why some people spend their money as soon as it hits their account. However, if you invest the same $1000 into a good investment, it will buy you more things and it will preserve its value through time. You can calculate how much your money will worth if you have the inflation rate percentage. For example, if the inflation rate is 3% in a year your $100 will worth about $97. The main reason why some people do not keep cash at home is that inflation will secretly make their money worth less and less. So the best practise is to keep your money in a saving account that pays you interest or in an investment that is good enough to preserve the hard earned money that you have. Money is a very complex topic but if you follow the known rules you can make sure you do not lose money which is the first rule of investing.