Affix, prefix, suffix? And whats the difference between these mods?

http://classic.battle.net/diablo2exp/items/magic/

knockback is no prefix / suffix / affix ... it is an inherit mod only on a few Set items (i can't remember if also unique...)
and it is part of a craft glove recipe (u can look it up) so gloves with that recipe will always spawn with KB

yes, uniques aswell i.e. Windforce

"of the bear" is a suffix that can spawn on regular rare and magic melee weapons and grants knockback