Need is called the painful sensation of lack or lack of something, this lack is of a physiological order, that is, of a material nature that man experiences as a requirement of life, which must be satisfied in order to survive and evolve.

When we know the object capable of satisfying the need, then that need generates a desire to obtain it.
The desire is psychological in nature and disappears as soon as the need is satisfied.
The importance of the study of needs lies in the fact that they are the beginning, origin and purpose of all activities and events in society.
In this process the following moments are fulfilled:
1st Painful feeling of lack or lack of something.
2nd Desire or precise mental representation of what is missing.
3rd Demand that drives effort or activity to achieve the desired object.
4th Satisfaction, man defeats nature and obtains from it the means that allow him to survive and evolve.
Example: In the need for food, the satisfaction process is:
2nd Desire: Food
3rd Requirement: Work to get food

4th Satisfaction: Eat


Needs can be classified from different points of view given their infinite number. We will classify it in two ways:

a) In the most usual way
a.1) Primary Needs:
They are biological needs, also called vital needs because the preservation of life depends on their satisfaction.
Examples: Food, housing, clothing, etc.
a.2) Secondary Needs:
They are needs of a human order or of a higher order typical of the human species. They are called that because their satisfaction is not essential for the preservation of life.
Examples: Recreation, culture, education, etc.
a.3) Superfluous Needs
Also called luxury needs, they are those that only serve to give us some comfort. Examples: Jewelry, automobile, yachts, etc.
Classify the needs:
b) Another more general classification:
b.1) Material needs:
Aimed at satisfying physical demands. Examples: Drinking, eating, etc.
b.2) Spiritual needs:
They are related to our inner life, such as culture, art, etc.
The needs have the following characteristics:
b) Limited in capacity
e) They can be replaced one by another
a) The number of needs is unlimited,

They vary infinitely from place to time. As man has advanced towards civilization, needs have increased.

b) They are limited in capacity or saturation, The intensity of the needs decreases as they are satisfied, until there comes a time when the painful sensation and the demand disappear. Example: To quench thirst, perhaps, we would drink no more than two glasses of soda.
c) They are concurrent, That is to say, all needs are presented together, this forces us to order them and satisfy the most pressing first, which in turn implies the sacrifice or postponement of others. Example: Need to have fun and study. We will have to prioritize.
d) They are complementary,

the satisfaction of a need that simultaneously satisfies several other minor needs that complement it. Example: The need to study requires a study center, books, tickets, photocopies, etc.

e) They can be replaced one by another,

since a need can be satisfied in different ways. We can replace the form of satisfaction with another. Example: Bread for toast.

f) They vary intensity, depending on the circumstances and according to the moment in which said need arises. Example: Having ice cream in summer or having it in winter.
g) Fixation, There are needs that need to be satisfied on a regular basis. Example: Smoking.
GOSSEN’S LAW: “Desire decreases to the extent that the need is satisfied.”

Man tries to satisfy his needs by acquiring goods.