Constitutional amendments are laws - big laws that make big changes. Amendments are laws that are added to the Constitution of the United States. The writers of the Constitution did not want to make adding an amendment impossible, just very tough. They understood that things change over time, and they wanted the Constitution to be able to carefully change as well, if enough people agreed a change was needed. To do this, they wrote how to add an amendment to the Constitution right into the Constitution, so there would be no confusion about what it would take to add or to take away any right or rights of the states or people of the United States of America.
Over 11,000 amendments have been introduced in Congress since the Constitution was first drafted. Out of the 11,000+ proposals, only 27 amendments have been approved, and the first 10 of those are called the Bill of Rights - the 10 amendments that were added to the Constitution before the states would ratify (agree to) the Constitution. Adding an amendment to the Constitution is a very big deal.
So what does it take to add an amendment? The answer is a great deal of time and discussion and a whole lot of people agreeing that this is something which simply must be done. In brief - 2/3 of the Senate and Congress must approve the amendment; then it is sent to the states to ratify, and 3/4 of the states must agree to approve it before it can be added to the Constitution. So far, not counting the Bill of Rights (the first 10 amendments), only 17 additional amendments have made it successfully through this process.