Okay kiddo, so an endling is a word used to describe the very last of a certain kind of animal or living creature. Imagine you have a big jar full of candy and you eat all the candies until there's only one left, that last candy is like the endlings. It's the very last one and there won't be any more left after that.
Now, animals also have endlings. Let's say there used to be lots of dodos, and they are all gone now, except for one lonely dodo bird which is now called the endling. It's the very last one alive and there won't be any more dodos in the world after it.
The concept of endlings is really sad because it means that a certain kind of animal or creature is at risk of extinction, which is when they are all gone forever. That's why it's important to take care of the animals and the environment around us so we can prevent endlings from happening.