How do you move a face without creating another faces? enter link description here

In shown image and video

Number 1 is the problem I don't understand.

Number 2 is the final result I wanted.(mirror modifier in it.)

Number 3 is to test and compare with Number 1

Whenever I try to scale the Number 1 up to Z, it also creates unwanted side faces around it(this happens a lot and always confuses me). But Number 3 scales up properly without creating ones.(Newest objects tend to not create those)

What is the difference between Number 1 and 3? What am I doing wrong?
There are multiple vertices on top op each other. Go into edit mode, select all (press a), and then open the tools panel on the left by pressing t. There's an option called "Remove doubles". Press that and you should be fine.