Cheeses in this category are often spread on bread or crackers to be served as snacks. They're usually not used for cooking. Most soft cheeses should be used within a few days of purchase--they spoil faster than firmer cheeses.
Most soft cheeses are made with cow's milk. Cheeses made with sheep's milk, like feta, Brinza, and ricotta salata, have more butterfat, which make them richer and creamier. Cheeses made with goat's milk, like Humboldt Fog, tend to have a tangy, earthy, and sometimes barnyard flavor.