Overkneading toughens the dough. Chilling the dough for 30 minutes to one hour before cutting the biscuits out helps, too. Cut straight down, don't twist the cutter or the edges of the biscuits seal and the biscuits won't rise as high. I've read a cake is a pastry but not vice versa and that cakes have sugar which pastries do not, but I've also seen many conflicting recipes. I'm thoroughly confused the more I think about it.
Some terms overlap in the food world.
In general terms, I think a cake can be thought of as a pastry and a pastry can often be a cake. To be a bit more specific, both pastries and cakes are usually made of a sweetened base that is baked. Most cakes are made of a batter or dough that contains a leavening agent that helps the batter rise, like beaten egg whites or baking powder. Most pastries are made with unleavened dough, using butter, lard or vegetable shortening, flour and some liquid for their base.