Gerrymandering: the redrawing of congressional districts by the majority party in the House of Representatives in order to form safe seats.
Safe seats: Seats in which 55% of the people in a district support the incumbent.
Incumbent: Elected official currently holding office.
With the vocabulary out of the way, I hope that you understand the importance of the issue. As I'm sure you know, the House of Representatives is the only part of government with officials voted for directly by the people. However, every 10 years with the census, the districts these officials represent are redrawn. When redrawn, the majority party makes it so the minority party loses representation by having a super-majority in some districts and just enough to lose in others, thus eliminating competitive elections.