What does the K value mean?

[argan719]

`void main()
{
string fileData = "D://Facade//data.txt";
string fileOut = "D://Facade//data";

// read in data
PointCloud<double> pointData; 
readDataFromFile( fileData, pointData );

int k = 20;
LineDetection3D detector;
std::vector<PLANE> planes;
std::vector<std::vector<cv::Point3d> > lines;
std::vector<double> ts;
detector.run( pointData, k, planes, lines, ts );
cout<<"lines number: "<<lines.size()<<endl;
cout<<"planes number: "<<planes.size()<<endl;

writeOutPlanes( fileOut, planes, detector.scale );
writeOutLines( fileOut, lines, detector.scale );

}`

What does the K value mean?
I have seen that the k value is used in other functions as well.
I'm curious about what k does and why it's set to 20.
And can better results be obtained by changing the value of k depending on the data used?