Small candies sold individually for something in the neighbourhood
of 5 cents. (Presumably they were closer to a penny
when the term was coined..) Penny candy
falls in to a few basic food group
(note: I am a canadian candy connoisseur. US candy varies slightly and international candy varies very significantly.)
Plain gummies & jellies: The archetypical gummy candy is of course, the gummy bear. Candies of this sort are smooth on the outside, sticky once you bite in to them, contain mountains of gelatin, and are very sweet and generally fruit flavoured. The gummy variety are very chewy and somewhat translucent; the jellies are easy to bite through and are more opaque. The archetypical gummy candy is of course, the gummy bear; other examples include gummy berries and cola bottles. Jelly candies include swedish fish, those little black jelly babies, awful tasting minty green thumbs, and DinoSours.
Sour gummies: These are gummy or jelly candies coated in sour crystally powder. The most popular are sour cola bottles, sour berries, sour gummi worms, and the ubiquitous sour soother.
Marshmallows: Marshmallow-esque candies. These are almost entirely limited to three types: red strawberries (well, squat pink marshmallow cones dusted in red sugar dust and ostensibly strawberry flavoured), bananas (dense yellow marshmallows - roughly a cross in texture and taste between real marshmallows and cereal marshmallows.), and orange circus peanuts (much like the bananas, though they tend to be a little chewier).
Marshmallow/gummy hybrids: Half gummy, half foamy candy. The chief example is marshmallow gummy frogs, but following their success, some others have come out, notably blue sharks and brains.
Wrappered candy: individually wrapped candies that are sold loose. Caramels, chewy fruit candies (MoJos, etc.), and bazooka gum.
Liquorice: liquorice isn't strictly speaking penny candy - it's more petty candy, really, but it's frequently lumped in to the penny candy category. Good old black and red liquorice is supplemented these days with more unusual flavours: wildberry, pink grapefruit, raspberry, disgusting chocolate tourist liquorice, and I even saw lemon liquorice the other day - tasted disturbingly like lemon meringue pie. O, what will they think of next..