Latino sine flexione is a type of simplified Latin language that uses words without any changes in form, like adding -s or -ed at the end of words, unlike English. It was developed by a linguist named Giuseppe Peano in the early 20th century so that people who spoke different languages could communicate easily without having to learn all the grammatical rules of Latin.
So imagine you have a toy car, and you want to play with your friend who speaks a different language. You both know the word "car," but your friend has a hard time remembering that in English, you say "cars" instead of just "car" if you have more than one. So you decide to come up with a new game where you use a simple version of English that doesn't add any extra endings to words. That way, it's easier for your friend to understand without having to learn all the complicated rules of English.
That's kind of what Latino sine flexione is like! It's a simplified version of Latin that doesn't use all the extra endings that can make it difficult to learn. Instead, all the words stay the same no matter what form they're in.