The 14th Amendment is important in the evolution of civil liberties because it was used to incorporate the Bill of Rights. What that means is that the 14th Amendment was used to justify the doctrine that the Bill of Rights (or at least some aspects of the Bill of Rights) applies to the states and not just to the federal government.
The Bill of Rights as it is written only applies to the federal government. For example, the First Amendment says (among other things) that “Congress shall make no law” abridging the freedom of speech. It clearly does not say that state legislatures could not make such laws. Before the 14th Amendment, then, the Bill of Rights did not apply to the states and they could make laws violating the Bill of Rights if they wished (and if their own constitutions did not forbid those laws).
The 14th Amendment says that states cannot “deprive any person of life, liberty, or property, without due process of law.” The Supreme Court ruled that this means the states cannot make laws that violate people’s liberties. The Court has ruled that various parts of the Bill of Rights (in fact, almost all of the Bill of Rights) are part of people’s liberties that cannot be violated by the states. This doctrine is called “selective incorporation.”
Thus, the 14th Amendment brought about the doctrine of selective incorporation, thereby setting the rule that most parts of the Bill of Rights apply to the states and not just to the federal government. This was a very important part of the evolution of civil liberties in the United States.
This second answer is correct, but as the question asked about civil liberties and not civil rights, I did not include this information. If your teacher cares about the difference between civil liberties and civil rights (which I do when I teach), do not include information about civil rights in your answer.
There is an important historical context to the Fourteenth Amendment, involving the Civil War and its aftermath. Additionally, it is good to understand how this amendment provided the basis for civil rights legislation in modern times.
The first aspect to note about this amendment is that it was passed in 1866, immediately after the end of the Civil War. This was by no means a coincidence. As the above response notes, the amendment takes some of the protections against the federal government afforded in the Bill of Rights and applies those protections to the actions of state governments, too. The reason for this was that the Southern states would or had already tried to prevent former slaves from being afforded many rights, with arguments, for example, that they were not citizens, thus not entitled to the various protections of due process or equal protection of state laws. (Southern states persisted in making life difficult for former slaves and other African-Americans for the purposes of voting, forcing the creation of the Fifteenth Amendment three years later, providing that race, color, or "former servitude" could not be used as reasons to prevent any citizen from exercising the right to vote.)
Second, at the very end of the Fourteenth Amendment is this statement:
The Congress shall have the power to enforce, by appropriate legislation, the provisions of this article.
Without this statement, African-Americans would have a right, but would have no remedy, just as the Emancipation Proclamation was merely a statement until the Thirteenth Amendment was passed. It is the final sentence in the Fourteenth Amendment that led to the passing of the Civil Rights Act of 1964. The Southern states, over the years, had persisted in passing any number of laws, collectively referred to as "Jim Crow" laws, all means of depriving African-Americans of many rights. Without the Fourteenth Amendment and its enforcement sanctions, Congress would have had no authority to pass the Civil Rights Act and would only have been able to ensure that the federal government act in accordance with the rights provided. (In the Fifteenth Amendment, the same statement at the end led to the Voting Rights Act of 1965.)
It should also be noted that in spite of the various civil rights problems for African-Americans in the United States, it took nearly one hundred years of pain and suffering before Congress acted, a sad commentary on the priorities of a country that is supposed to have been founded on principles of freedom, justice, and equality.
The 14th amendment is a very important amendment that explains what it means to be a US citizen and protects many of the rights of the people. There are three main clauses in the 14th amendment. The first one is the Citizenship Clause. The citizenship clause gives individual born in the United States the right to be citizen including African Americans. Clause two is the Due Process Clause. The due process clause protects the 1st amendment rights of the people and prevents those rights from being taken away by any government without “due process.” Due process is a trial by jury for all people accused of breaking a law. The final clause is the Equal Protection Clause. This part of the fourteenth amendment states that there may be no discrimination against them by the law. The equal protection clause extended this protection to the state governments. This clause of the 14th amendment would later be used to end discrimination and segregation in the South. The 14th amendment was important in bringing the Confederacy back into the United States after the Civil War. The US took responsibility for the pensions for soldier that had fought in the war and refused to take on the Confederate debts, while also preventing former Confederate leaders from holding elected office or civil positions.The 14th amendment also ensured that debts due to the emancipation of slaves were “null and void” (not allowed).