Confusion about bian 邊 and miàn 面
To understand the differences properly, you need to know what is 面 and what is 边. 面 is a face whereas 边 is an edge. An edge is like a line guiding you the direction. A face is what is facing you giving you a sense of position.


前/后面 is used to describe the position of something within your visual range. Whereas, 前/后边 is more appropriately used to describe
something beyond visual range when giving directions.


  镜子前面 (in front of the mirror) vs 车站前边 (beyond that bus stop in front)

外/里面 is used to describe location of an object in relation to another object. 外/里边 is used strictly
for giving directions.


  书包里面 (inside the school bag) vs 巷子里边 (in that alley)

左/右面 is used mainly to point to the left or right face of an
object. 左/右边 is used to describe left or right side directions.


  墙的左面 (on the left face of that wall) vs 车道左边 (left side of the
  roadway)



In summary, when you are giving directions, use 边; when you are describing positions, use 面.