Nearly everything you’ll do nowadays costs money. From basic constant costs, like groceries or rent, to surprise expenses, like medical bills or parking tickets. It’s extremely difficult to be able to exactly predict surprise expenses. That’s the whole point- they’re surprises; you’re not trying to get sick on purpose. Because you can’t exactly budget for these things, you can save money to use it later. Crazy concept. 

There are two main types of emergency saving. There’s a rainy day fund, which is for smaller expenses like small medical bills, home maintenance, or parking tickets. The second is a straight up emergency fund that involves larger expenses like large medical bills or loss of income. Technically, the rule of thumb is that you should have 3 months worth of living expenses saved- but in reality, for most Americans, that is not the case- being alive is expensive. A lot of people start their careers with hourly pay jobs, sometimes, when they’re older or have achieved higher education, they switch from hourly to salaried pay. This can be challenging for some. They might be used to picking up an extra shift to pay for the parking ticket for example. Saved money would help make the transition easier. In terms of non-emergency saving reasons- you might want to save for larger purchases that can’t be covered in one paycheck- like a down payment on a house or a car.