Soft tofu (嫩豆腐 or silken tofu), as its name suggests, is a softer version of tofu. It is undrained, unpressed and has a high moisture content. Its moisture content should be taken into consideration when added to recipes. It is often used to make sauces, or smoothies.
Tofu is prepared by coagulating soy milk and pressing the resulting curds into a solid block of varying softness (silken, soft, firm, extra firm etc). Tofu has a muted flavor, that can be used in both sweet and savory recipes. Tofu is low in calories, and is a rich source of protein, iron and calcium (if the tofu was calcium-set).
Tofu is set using a variety of coagulants, like gypsum (calcium sulfate), which produces tofu that is tender but brittle in texture, and chloride-type nigari salts (magnesium chloride and calcium chloride), which produces tofu with a smooth and tender texture.
There are many types of processed tofu, including pickled tofu (sticky tofu, pickled tofu) and frozen tofu (thousand-layer tofu, kori tofu). Tofu byproducts are also very popular, and this includes tofu skin (yuba) and soy pulp (okara).