The default interface command erases all commands on the particular interface places the interface in a default state which includes no shutting the interface.  Below is the configuration of an interface before and after running the default interface command.
Sales2#show run interface fastEthernet 1/0
Building configuration…
Current configuration : 128 bytes
!
interface FastEthernet1/0
description Dev Lab
ip address 192.168.3.34 255.255.255.0
shutdown
duplex [...]