What is umbilical cord clamping?

You might need to look up some websites if you want to write a report on any topic.

Short version, baby is born, cord is cut, then clamped to stop stuff coming out of or into the cord.

What level is the report? Start with wiki, then google it and have a read of a few website, then (if the report is senior highschool or higher) jump on google scholar and review some journal articles.