allowfullscreen="allowfullscreen"

I do use H5P with wordpress.

If I copy and paste the iframe, i have several lines of code, the width, height, frameborder and allowfullscreen="allowfullscreen"

Which is the purpose of allowfullscreen?

Must I use it? or in order to make a simplification of the code, i can take it off as like with the width, height, frameborder (which i no longer use in my code)