Difference between afforestation and reforestation
Afforestation is the process of establishing forests in areas that have never been forested. If you plant trees in an area, like a dry land, which was never a forest, this process is afforestation.
Reforestation is the restoration of forests in areas where forests were removed or destroyed. If you plant trees in an area, which was a forest but was destroyed by cutting off trees etc, this process is called reforestation.