Supreme Court alters the Voting Rights Act

Despite what you may have gathered from some of the overwrought headlines I've seen on social media, the Supreme Court did not invalidate the Voting Rights Act Tuesday. But it did make some key changes to the way the Act currently functions. Here's Amy Howe of the SCOTUS Blog, explaining the ruling in plain English (as opposed to legal speak, which is kind of a different language):

Today the Court issued its decision in Shelby County v. Holder, the challenge to the constitutionality of the preclearance provisions of the Voting Rights Act. That portion of the Act was designed to prevent discrimination in voting by requiring all state and local governments with a history of voting discrimination to get approval from the federal government before making any changes to their voting laws or procedures, no matter how small. In an opinion by Chief Justice John Roberts that was joined by Justices Scalia, Kennedy, Thomas, and Alito, the Court did not invalidate the principle that preclearance can be required.
But much more importantly, it held that Section 4 of the Voting Rights Act, which sets out the formula that is used to determine which state and local governments must comply with Section 5’s preapproval requirement, is unconstitutional and can no longer be used. Thus, although Section 5 survives, it will have no actual effect unless and until Congress can enact a new statute to determine who should be covered by it.

Basically, this is the court saying that the parts of the country that needed preclearance applied to them in 1964 might not be the same parts of the country that need it today, and they've kicked the law back to Congress to decide how to deal with that.
In theory, this could be a good thing. Obviously, racism still exists. But it's also reasonable to assume that the practical application of racism on voting rights might look different than it did half a century ago. Some places that had big issues with this in the 20th century might not today, and vice versa.
The downside, though, is the reality that the Supreme Court just handed the ball to Congress — that is to say, it's now the responsibility of a spectacularly fractured institution that can't seem to get even basic budgetary measures passed, let alone something as inevitably controversial as new rules for Voting Rights Act preclearance. And, without that, the whole part of the VRA that is supposed to prevent discrimination in high-risk areas is dormant. It just sits there — a nice idea, and one the Supreme Court says they technically agree with, but now completely lacking any power.
It's not the same as completely wiping out the VRA, but it does change the way the VRA works (at least until Congress acts) in ways that make it harder to prevent voter discrimination. People can still challenge local changes to voting districts or rules under the VRA, but now it's their job to prove that the VRA has been violated — rather than the state or district's job to prove that it has not.