Gerrymandering may sound like a silly word, but it's serious stuff. The issue that was enough to bring Barack Obama back into politics in March 2017 is back in the news following a 5-4 Supreme Court ruling that the practice isn't unconstitutional and, therefore, can't be challenged in federal court. That means Republicans, the main beneficiaries of gerrymandering in recent history, can continue to do so.

Wondering what exactly gerrymandering is, aside from being a word you remember hearing in your AP history class? Here’s what you should know about the issue.

What is redistricting?

Before we get into gerrymandering, we have to talk redistricting, which is at the core of the issue and important in determining who represents you in Congress.

Each state is partitioned into territorial divisions that contain a more or less equal number of constituents. These partitioned areas are known as congressional districts, and each elects one representative to serve his or her constituency in the U.S. House of Representatives. Redistricting is the process of redrawing the boundaries that determine congressional districts in each state, in order to balance the population among districts. The process takes place every 10 years, typically following the government census. Although redistricting occurs nationwide, the actual process varies by state. Michael Li, senior counsel of the Democracy Program at New York University’s Brennan Center for Justice, a nonpartisan law and policy institute, tells Teen Vogue that in most states the maps are drawn by the politicians in the state legislature (sometimes with the help of advisors) and signed off on by the governor. In some states, though, independent and bipartisan commissions draw the maps instead. You can see which state uses which process on this map from Loyola Law School, Los Angeles, professor Justin Levitt.

The point of redistricting is to ensure that every voter has an equal say by creating equal-population-size districts — but that’s not usually the end result. “It is unfortunately a process that oftentimes becomes politicized and an opportunity to try to manipulate the maps, rather than simply to draw fair maps,” Li says. And that’s where gerrymandering comes in.

What is gerrymandering?

Broadly, gerrymandering is when one political party redraws the boundaries to give it an advantage over its opposition. “There are a bunch of redistricting abuses that get clumped together under ‘gerrymandering,’” Li says. “You can think about them all as real harms...but they all have very different causes and they all have very different symptoms and they all have very different cures.”

One manifestation of gerrymandering occurs when the majority party in a state legislature manipulates district boundaries so that voters for the opposing party are either dispersed throughout the state so they won’t make up a majority in any district, or packed together in a minimum number of districts and don’t have enough representation in other districts to win the majority of the state’s House seats.

Gerrymandering can also be used to protect incumbents, such as when legislators create districts that strategically group together supporters of sitting representatives to minimize competition.

And then there’s racial gerrymandering, or when district lines are intentionally drawn to disperse minority groups, to dilute their influence in a district, thus making it impossible for them to elect representatives. “In other words, [it’s] ensuring that African-Americans or Latinos or other communities of color don’t have a sufficient seat at the table,” Li says. The Voting Rights Act of 1965, which outlaws discriminatory voting practices, prohibits redrawing districts for the purpose of minimizing the influence of racial minorities. Li also explains that in states where there tends to be “racially polarized” voting (meaning minority voters prefer different candidates than white voters do), the Voting Rights Act requires the drawing of majority-minority districts (meaning the majority of people within those districts are minorities), as long as those districts can be geographically “compact.” But drawing majority-minority lines can serve to disadvantage minority voters when “packing” them into just a few districts limits their influence in the rest of the state.