Dear Aspirant

Weightage in marks in an exam is the quota assigned to a particular segemnt as this time, 40% weightage would be given to 12th marks n JEE Mains. ... here, the rest 60% will be from the JEE exam.

On the other side

weight certificate is a rural area residence Certificate which is a  proof to ensure that the person bearing the certificate is a Resident of the village of District / State by which the Certificate is being issued.

Best Wishes.