Today the Supreme Court issued two historic rulings related to marriage.
The first was on the Defense of Marriage Act, which the Supreme Court has deemed unconstitutional based on the concept of equal protection under the law. Therefore the federal government must provide homosexual couples the same benefits afforded to heterosexual couples, so long as the homosexual couple has been married in a state where gay marriage is legal. It does not, however, legalize gay marriage nationwide. Whether or not you agree with gay marriage is a different issue entirely. What we have here is the federal government recognizing the need to treat every American equally under federal law.
The next big opinion handed down today by the court was related to Proposition 8 out in California. This one is a bit trickier to explain. Here's a very rudimentary explanation. California held a referendum (referred to as Proposition 8) and the voters voted to ban same sex marriage. A court then overturned Proposition 8, arguing that it violated due process and equal protection. Supporters of Proposition 8 then brought the case all the way to the Supreme Court. What happened today is that the Supreme Court ruled that the supporters who brought the case did not have the legal standing to appeal the court's ruling, and therefore the lower court ruling in California stands. In other words, same sex marriage is legal in California. And now, thanks to the Supreme Court's decision on DOMA, the federal government must treat any same-sex married couples in California the same as it would heterosexual couples.