Apart from the smaller chainrings, the BCD (bolt circle diameter) is smaller. Standard chainsets are usually 130 and 135mm, but compacts are 110mm (I think). This precludes fitting compact chainrings onto a standard chainset to get the benfit of lower gearing in this way. I understand that the smallest inner chainring you can fit on a standard set has 38 teeth, but compact inners are often 34 teeth.
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Yes, it does have smaller chainrings. Usually 50-34 as oppossed to 53-39 on a, so called, standard crankset.