A non-excludable good is a good that can be used by everyone because price doesn't restrict access to the good. Things like public parks and roads are often considered non-excludable goods.
Sometimes, things labeled non-excludable are not truly non-excludable. For example, some public parks charge an entrance fee and have fences preventing entrance, which excludes some people from using them. Many roads throughout the United States charge tolls for either pedestrians, automobiles or both.
Non-excludable and excludable goods can fall into different categories. Public common goods, such as fishing grounds, are often non-excludable because they are open to the public and free to use. The national defense system, mail system and the court system are examples of pure public goods.
Sometimes, a good can be both non-excludable and excludable. Examples of this would be radio and television stations. Some stations are accessible to everyone and others like XM/Sirius and cable are paid services that exclude those who cannot or choose not to pay for them.
Excludable and non-excludable goods also fall into the categories of rivalrous and non-rivalrous. A good is considered rivalrous when it can only be consumed by one person at a time. A non-rivalrous good may be consumed by several people at the same time at no additional cost.