technically
the vistor can add to the wp_term talbe a record like
term_id(auto insert)/name/slug(auto insert)
auto(for example 123)/"USA"/"usa"
at the same time add to the wp_term_taxonomy
term_taxonomy_id 123
term_id 123
taxonomy student_comefrom
description any
parent 0
count any
I hope MetaBox can help
PS:I have brought all the plugs
