Recipe Talk

do they mean plain flour or self raising?

All purpose means it can generally be used for most recipes calling for "flour" - it has no additional ingredients. Self-raising has raising agents already added (salt, sodium bicarb, etc.).
Pastry flour is more finely ground than all purpose flour and has a low gluten content, produces lighter baked products. Bread flours usually have extra gluten to produce more elastic dough - good for bread, less good for baking.

in U.K. & OZ & nNZ. it is known as plain flour.
Bunyip in OZ