Can anyone tell me what the differences are between 2 and 4 stroke pluggs???

Some 4 stroke plugs have an extended unthreaded snout so they can project further into the combustion chamber but the main difference is that they're classed as a much hotter plug than the usual 2 stroke hot plug. This is so they'll continue to glow at idle when there's twice as much time for them to cool down between power strokes. Because they're such a hot plug they're useful in some 2 strokes running zero nitro fuel, very rich mixtures or high oil content.