Farsight Alteration ward - Please explain it to me.

I'm not really understanding what it does or how to use it.

It says your cast range is expanded 650 percent. What does that include? Is it only magic? So, for example, if I use Jhin or MF who dont have magic, it won't be helpful?

How do I know what it effects?

Do you have to be standing inside the ward area circle for the range to be effective?

Any other tips?

Thanks for the help.