Coronaviruses are a large family of viruses. Some cause illness in people and others cause illness in animals. Human coronaviruses are common and are usually connected with mild sicknesses, almost the same as the common cold.
COVID-19 is a new disease that has not been (before that/before now) identified in humans. Rarely, animal coronaviruses can infect people, and more rarely, these can then spread from person to person through close contact.