It does not mean columns, it is showing the same behaviour, to create a vector of columns to be selected
data[row, c("columnname1", "columname2",....)]
data[row, c(1,3:5,7,....)]
And it works the same with rows
data[c(1,4,5:9), c(1,3)]
For selecting rows 1,4,5,6,7,8,9, and columns 1 and 3
You use 'c' to select more than 1 row or columns, by names or position (numbers) with the exception of consecutive ones, like
data[5:9, 2:4]
Where you select rows 5,6,7,8,9 and columns 2,3,4.