Most commonly used in mathematics to refer to the four quarters of the coordinate plane.
Recall that the coordinate plane has an x-axis that divides into a top and bottom half, and a y-axis dividing into the left and right half. Together they create the four quadrants of the plane. By convention they are numbered one to four, the first quadrant being to the top right, and then going counter-clockwise from there
Also by convention they are often numbered using Roman numerals: I II III IV.