While they're "technically" different, there's not really regulation...almond extract is usually of higher quality, especially when it's pure. "Essence" can really be made of anything, as long as its almond-y.

Is that the same as Almond Extract? BB

Here in Chicago you can find it in most supermarkets but you'll probably get more bang for your buck in a Middle Eastern/Mediterranean market. If not available to you, try amazon.com