Equal Protection Clause

The Equal Protection Clause is part of the Fourteenth Amendment to the United States Constitution. The clause, which took effect in 1868, provides that no state shall deny to any person within its jurisdiction "the equal protection of the laws". 
Meaning.
A primary motivation for this clause was to validate the equality provisions contained in the Civil Rights Act of 1866, which guaranteed that all people would have rights equal to those of all citizens. As a whole, the Fourteenth Amendment marked a large shift in American constitutionalism. It applied substantially more constitutional restrictions against the states than had applied before the Civil War.
The meaning of the Equal Protection Clause has been the subject of much debate. It has inspired the well-known phrase "Equal Justice Under Law". These words are inscribed on the U.S. Supreme court building. This clause was the basis for "Brown v. Board of Education" (1954). This Supreme Court decision that helped to dismantle racial segregation, and also the basis for many other decisions rejecting discrimination against people belonging to various groups.
State vs federal governments.
The Equal Protection Clause itself applies only to the federal government. However, the Supreme Court held in "Bolling v. Sharpe" (1954) that equal protection requirements apply to state and local governments through the Due Process Clause of the Fifth Amendment.