I think many already know that in Minecraft PE added console command, which is detailed enough where it is written. In this guide I will try more to describe the essence of each commands.
So, the full list and a note for each commands: /? or /help - help command reference. Print the full list of commands in multiple pages.
/clone - copies a region from the first two coordinates in the third.
/gamemode <0/1> - set player survival mode(0) or creative mode(1).
- - give items.
/kill - kill player. (you can't kill the player in creative mode)
/list - show list of players connected to the server.
/op - gives the specified player operator.
/deop - to take the player to the operator.
/say - write something in the chat.
/setblock - set the block at the specified coordinates.
/setworldspawn - set the spawn for all players.
/spawnpoint - set the spawn for the player.
/summon - spawn a creature by the coordinates (for example, /summon lavaslime 5 5 5).
/tell (or /w, /msg - send a message to the player.
/time add - add time (to rewind).
/time set - set time. (for example, /time set day or night)
/toggledownfall - to turn on/off the rain.
/tp or /teleport - teleport to coordinates.
/tp or /teleport - teleport a specific player to the coordinates.
/tp or /teleport - teleport to player.
/tp or /teleport - teleport to player_1 player_2.
/xp - gives specified player experience.
/fill - fill the selected area with blocks.
Yet some commands about which I wrote above: