Your GPA is your grade point average, and it is a number that indicates how well you score or perform, on average, within your courses and degrees. In many university degrees, a higher GPA will improve your chances of getting hired for certain jobs, as it shows that you performed better on average, and you somewhat excelled in the area of expertise that they are looking for.
Coursera, however, does not affect GPA. The grades you get during the Coursera course do not matter, it is all about the final certificate that proves you finished the course.