An obit is a news story about someone who's recently died, usually including details about the person's life and the date of their death. You can also call an obit a "death notice."
Obit is a commonly used informal name for an obituary. Traditionally, obits were published in newspapers either daily or weekly, while today they're just as likely to be published online, often posted by a funeral home or church that's hosting memorial services. Obit comes from the Latin obitus, "death," the past participle of obire, "to go toward" or "to die."