What are the differences between phosphorylation and dephosphorylation?

Phosphorylation and dephosphorylation are two types of enzyme catalyzing reactions that involve phosphate groups. Both are essentially counterparts of each other. 

In the phosphorylation reaction, a phosphate group is added to a molecule. The reaction is catalyzed by the enzyme protein kinase. 

In the dephosphorylation reaction, a phosphate group is removed from a molecule. The reaction is catalyzed by the enzyme phosphatase.