The Constitution can be amended in two ways. The first way is through a two-thirds majority vote in both the House of Representatives and the Senate. The second way is through a national constitutional convention called by two-thirds of the state legislatures.
An example of why the Constitution would need to be amended is to address social changes or injustices, such as the addition of the 19th Amendment, which granted women the right to vote, reflecting the evolving understanding of civil rights and equality.