Endangered means to be under threat or near extinction. When a species/animal is endangered it means that they are disappearing fast or have a very small population - not large enough to survive. Extinction means the end of existence for a species.
The IUCN (International Union for the Conservation of Nature and Natural Resources) have what is known as a Red List. This red list is a guide to how endangered a species is - animals are measured on a scale from 'Least Concern' to the worst 'Extinct'.Read More: Endangered Animals