You need a new pair of shoes. You have a specific amount of money you can spend. Will you spend every last penny on one pair of shoes, or will you exhibit thriftiness and have money left over after your purchase? Thriftiness amounts to using money and other resources carefully rather than wastefully. We most often use the term to mean spending only what is necessary. To be thrifty is to be frugal; some might even use the word cheap. The opposite of frugality is extravagance.
Our society as a whole has a problem with money. Many people spend more than they have. Shopping has become a favorite pastime that leaves people with empty pockets, purses, and bank accounts. Even the government spends more than it takes in! Families are destroyed by debt - that is, by owing money that they don't have. Then when an emergency comes along, there is no money to take care of it.
While thriftiness can be taken too far, becoming stinginess, it's still a helpful character trait to develop. Having enough money to cover your current expenses is good, but having extra money saved up for future needs is even better.