The first step in making cheese is separating milk into two parts - curds (the milk solids) and whey (the liquid left behind). There are three main ways of doing this: using a starter culture of bacteria, adding rennet to the milk, or using acid. The curd is collected together and pressed firmly. The remaining whey then flows out, and the curds tangle better together. The cheese gets its round shape here. The cheesemaker only performs this step for hard cheeses. Soft cheeses are not pressed and, therefore, contain more moisture (whey).

Source: Food Unfolded