Athelas is a fancy way to write words on a computer. It's like fancy lettering that makes words look pretty and special.
Think of it like this: when you write your name on your paper in your normal handwriting it looks okay, right? But then when you try to write your name again but in your fanciest handwriting, it looks really special and important! That's what Athelas is like, but for a computer.
It has swoops and curves that make it look elegant and fancy. It's like the "dress up" version of writing words on a computer. It's not used for everything, just certain things like fancy invitations or special headings.