Not all mushrooms have gills under their caps. The one at the right obviously has pores, and spores fall from those pores the same way they do from gills on gill fungi. The pore fungus in the picture is a member of a large, common mushroom genus worth knowing, that of "the bolets," of the genus Boletus. One reason to know this genus is because it is common, and another is because many species in the genus are good to eat! This particular bolet, by the way, shows an important characteristic that some bolet species show. That is, its flesh "bruises blue." That dark splotch on the cap's top right is the "blue bruise." A few seconds before I pressed my thumb there, that area was yellow like the rest of the cap. Many bolet species do not bruise like that.
Some pore fungi grow quite large, such as the above, on a tree in Chicago. This is Polyporus squamosus, which gets nearly a foot across (30 cm). This fungus is edible but it's so tough that few mushroom eaters bother with it unless they find very young bodies. The species grows on dead wood. The host tree is living, but it can be seen that the fungus body emerges from a crack in the tree's trunk, so the fungus's hyphae must be coursing through dead wood inside the tree.
One of the most commonly encountered pored fungi is shown at the left. It's name is Turkey Tail (wonder why?), Trametes versicolor. This fungus is so tough and leatherlike that there's no question about eating it. You can find this species on wood throughout the year, even in the winter.