Legit question, what on earth is this (for)? I tried reading the book a bit and it seems like a library for turning ml models into C code? But its really not

Legit question, what on earth is this (for)? I tried reading the book a bit and it seems like a library for turning ml models into C code? But its really not clear what the point of this book is about...Is this written by space aliens or is this a technical manual for chemistry? I have coming up on a decade of Python, Java, JS experience, I know what programming is, I don't know what this...thing...is for.