Answer:
Maslow was an American psychologist well-known by his humanistic psychology in his works. Probably the most known of his researches is relate with his hierarchy of needs, which according to Maslow is a theory of human motivation to achieve goals. This pyramid (image attached) shows from basic needs, which are for physical survival, to self actualization which are fulfilment needs.
In this way, Maslow said that there are mandatory needs for us, but not all of the needs shown in his hierarchy have to be achieved. In the case of biological needs, they are mandatory, because the need of food water is to keep alive the body, so, basically, we could die if we don't achieve this physiological needs.