a world of difference

US /ə wɜːrld əv ˈdɪfərəns/
UK /ə wɜːrld əv ˈdɪfərəns/
"a world of difference" picture
1.

a very great difference

:
There's a world of difference between knowing about something and actually experiencing it.
Living in the city and living in the countryside is a world of difference.