Social conflict is as natural and as socially beneficial as cohesion. Like cohesion, it can become harmful such as when it leads to violence.
Some conflict comes about when individuals and groups pursue incompatible or competing goals.
Some social conflict is rooted in social structure—driven by reward systems that create and perpetuate illegitimate inequalities (rewards not based on talent and achievement but on social characteristics like gender and race/ethnicity). The classic analysis of this form of conflict came from Marx who said that the history of all societies is the history of class conflict. This conflict is the conflict of competing interests.
Some conflict is socially constructed for some social purpose, such as to create and perpetuate inequality. For example, racism and sexism are value systems that allow men and whites to disadvantage women and people of color. Social conflict may be constructed for political purposes, as well.