The phrase "shed light on ___" means to explain or give information about something that people don't know much about.

For example, if there's something broken in your house and you think that your children may have caused it, you can ask them:

The lamp seems to be broken. Can anyone shed some light on what happened?

News stories often use this expression in headlines. For example:

Testimony sheds light on politician's shady dealings

This means that the things that people have said in court ("testimony") has shown some of the dishonest ("shady) things that the politician did.