Private Goods vs Public Goods

Public goods cannot or do not exclude non-paying users and your consumption does not reduce others' consumption.

private goods (demand for)
The demand curve for private goods is a horizontal summation of individual demands because consumption of private goods is subject to rivalry.
private goods
Goods that are subject to consumption rivalry but can easily exclude non-payers.
public goods
Goods that are not subject to consumption rivalry but cannot easily exclude non-payers either by design or due to technical difficulty.
public goods (demand for)
The demand curve for public goods represents a vertical summation of individual demands because consumption of public goods is not subject to rivalry.