Rabbi Kagan wrote a book, the Chofetz Chaim, his classic work on the laws of loshon hora, and generally became known as 'the Chofetz Chaim'. Guard your tongue from evil and your lips from speaking deceit. Learning the laws of Shmiras haloshon every day, in small portions, was the method that the Chofetz Chaim recommended for every Jew to observe this crucial mitzvah. False derogatory statements are called 'motzei shem ra' or slander. A statement which is not actually derogatory but can ultimately cause someone physical, financial or emotional harm is also loshon hora.
Hurtful words spoken directly to a person are another form of loshon hora.
It is loshon hora to humorously recount an incident that contains embarrassing information about a person even if there is no intent to cause harm or humiliation. Loshon hora is forbidden even if you incriminate yourself. To speak against a community as a whole is a particularly severe offense. Harmful remarks about children are also loshon hora. Loshon hora cannot be related even to close relatives.