What is natural vegetation?

Plants that were planted/grown without the assistance of humans would be considered natural vegetation.

Explanation:

Rainforests are the most common examples of natural vegetation; rainforests are usually uninhabited by humans which means plants find their own ways to grow. Animals take fruit off trees, eat the fruit leaving the seeds behind and then the excessive rain allows that seed to grow. That is natural vegetation "plants that were planted/grown without the assistance of humans."

Hope this helps.