People cannot be excluded from using public kids while they can be excluded from using individual goods.
A Public good can be used by everyone without exclusion or rivarly. For example: my consumption of a public good would never affect other people's consumption. Going for a ride in a public park would exemplify it perfectly. If I go for a ride in a public park would not affect the the right of another person to do the same thing. In the other hand, a private good is reserved for the consumer individually, it is excludable because it can restrict another consumers from using it, for several reasons as payment exchange, and it is rival due to limited quantity. Example: not everyone can buy a car due its price. Some people can do it, other people cannot, due to their purchasing power. If a car company of a certain brand manufactures a limited quantity of cars, not everyone could buy it for there would not be enough cars for a massive demand. That defines the rivalry.
