The United States Constitution has a provision called the "Full Faith and Credit" clause. Under Full Faith and Credit each State is required "...to recognize and give effect to valid judgments rendered by the courts of its sister States." (V.L. at p. 3).
The U.S. Supreme Court (aka SCOTUS) has issued several decisions affecting LGBT rights over the years. The last big one was Obergefell v. Hodges in June 2015 when the court decided that marriage equality could not be denied to same-sex couples. The V.L. v. E.L. decision runs along the same track but it addresses an issue on which SCOTUS has been silent--the right of same-sex parents to be legally recognized.
The V.L. decision is important because it removes any doubt that the Full Faith and Credit clause applies to adoptions involving same-sec parents. It also clarifies that one state must honor adoptions granted in another state even when there is disagreement.
This decision will provide considerable peace of mind to many same-sex couples and their children.