whats the use of commented line in my code please explain in details - find

Question

#the problem is why i used GCD (find the max point of a straight line). I can find out the slope by #doing m = (y2-y1) / (x2-x1), then whats the purpose to use gcd?
def lineThroughPoints(points):
maxNumberOfPointsOnLine = 1
for idx1, p1 in enumerate(points):
slopes = {}
for idx2 in range(idx1 + 1, len(points)):
p2 = points[idx2]
rise, run = getSlopeOfLineBetweenPoints(p1, p2)
slopeKey = createHashableKeyForRational(rise, run)
if slopeKey not in slopes:
slopes[slopeKey] = 1
slopes[slopeKey] += 1
maxNumberOfPointsOnLine = max(maxNumberOfPointsOnLine, max(slopes.values(), default=0))
return maxNumberOfPointsOnLine
def getSlopeOfLineBetweenPoints(p1, p2):
p1x, p1y = p1
p2x, p2y = p2
slope = [1, 0] # slope of a vertical line
if p1x != p2x: # if line is not vertical
xDiff = p1x - p2x
yDiff = p1y - p2y
gcd = getGreatestCommonDivisor(abs(xDiff), abs(yDiff))
xDiff = xDiff // gcd
yDiff = yDiff // gcd
if xDiff < 0:
xDiff *= -1
yDiff *= -1
slope = [yDiff, xDiff]
return slope
def createHashableKeyForRational(numerator, denominator):
return str(numerator) + ":" + str(denominator)
def getGreatestCommonDivisor(num1, num2):
a = num1
b = num2
while True:
if a == 0:
return b
if b == 0:
return a
a, b = b, a % b
points = [[1, 1],[2, 2],[3, 3],[0, 4],[-2, 6],[4, 0],[2, 1]]
print(lineThroughPoints(points))