Maslow's 'Hierarchy of Needs' concept is most easily described as a pyramid. Maslow's theory is that human beings cannot focus on or meet higher level needs before the more basic needs are met.
The bottom most level represents the most basic needs that a human being has: water, food, shelter, sleep. The next level defines the human need for a safe and secure environment. The third, or middle level, is social needs--friendship, family, romance.
The top two levels represent esteem and self-actualizing needs. At the highest levels, humans focus on their self worth and accomplishment as well as the desire for personal growth and meeting their potential.
In the classroom, teachers should consider their students' ranking on Maslow's 'Hierarchy of Needs,' particularly if that student is not performing well or seems to be struggling. Is he or she consistently not completing their homework? Maslow's hierarchy might offer insight into why that student is not meeting their full potential. If a student is consistently coming to class hungry or sleep-deprived, their most basic needs at the bottom of the pyramid are not being met, so he/she is really not going to be that attuned to your lesson for the day.
Maslow's 'hierarchy of needs' definitely offers insight into student motivation and psychological/physiological needs in the classroom.