A more thorough explanation:

The incorporation doctrine is a constitutional principle that applies parts of the Bill of Rights to the states through the Due Process clause of the Fourteenth Amendment. Before the doctrine's existence, the Bill of Rights only applied to the federal government and federal court cases. However, after the passage of the Fourteenth Amendment, the Supreme Court found that the Due Process clause included applying parts of the Bill of Rights to states.

Under selective incorporation, the Supreme Court incorporated certain parts of certain amendments, rather than incorporating an entire amendment at once. For example, the First Amendment has been fully incorporated, while the Third Amendment has not been incorporated at all. The Second Amendment has been fully incorporated, but the Sixth Amendment has only been partially incorporated.

One example of incorporation is the right to keep and bear arms, which was fully incorporated under the Second Amendment in the case of McDonald v. Chicago. Another example is the right to a speedy trial, which was partially incorporated under the Sixth Amendment in the case of Klopfer v. North Carolina.

It's important to note that not all amendments have been incorporated, and it's unlikely that they ever will be. For example, the Tenth Amendment directly interacts with state law, and the Supreme Court rarely relies upon the Ninth Amendment when deciding cases.

Overall, the incorporation doctrine is a way to ensure that the Bill of Rights applies to both the federal government and the states, protecting the rights of all citizens.