French dressing is vinaigrette, yes? What's Italian dressing?
I'll not assume what vinaigrette is in the UK, so I'll describe both. Italian dressing is closest to what I'd call vinaigrette. It's a mixture of vinegar (usually wine vinegar, occasionally balsamic) and oil, with some herbs and spices mixed in. French dressing is a somewhat sweet, somewhat tangy, orange colored tomato-based dressing, although there's a significant number of wide variations.

The Wish-Bone salad dressing company has a good overview of their salad dressings, which, I think, ignoring their brand-specific products, represents US expectations fairly well.
    I always reply "over easy", but that's only because I can't remember what the other way up is called.
``Sunny-side Up''. Precious, isn't it?
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Bitt Faulk