Difference between Rowcommand and Row DataBound

RowCommand event fires when a button is clicked from inside the GridView Row. 
Can be used to Delete, Update, Select, Insert (Yes, you can add insert functionality too into the GridView.

RowDataBound event fires when the data row is bound to the data source of the GridView. 
Can be used to customize the look and feel of the GridView rows or bound any custom data based on some other data to the GridView rows.