[Fontconfig] I'm wondering about binding"strong|same|weak"

[Mait]

Hello,

I only know should use "strong" or "same" for font substitution.

<alias>, <prefer> or <match> <test target="pattern" name="family" ....

I've read whole fonts-conf man page. But I don't understand about these well.

Please explain me like I'm 5! :)

When should I use strong|same|weak?

Thanks.
-- 
Mait