Difference between pcl::setRANSACOutlierRejectionThreshold and pcl::setMaxCorrespondenceDistance

I'm using the PCL library to do regitration between two point clouds but i did not catch what is the difference between this two parameters setRANSACOutlierRejectionThreshold and setMaxCorrespondenceDistance in the ICP process. The two of them are doing some rejection of outliers or false correspondence. Is it just the difference in the method used for the outliers rejection ? if its the case why in some implementation i see the people use both of them ?

Thank you