If you want to display rows without anything fancy, or any particular design, you would use BoundField. However if you would like to design the displaying of the record in a different manner than the default - you would need to create your own row template, by using the TemplateField.
Check out these links - they briefly explain the differences, but it is basically default VS customised presentation. http://forums.asp.net/t/1369418.aspx?boundfield+vs+template+field+in+gridview http://www.c-sharpcorner.com/Interviews/answer/1751/difference-between-boundfield-and-templatefield