Help

/help [CommandName]
Provides more information on the given command.

Give

/give [Amount] [DataValue]
Used to give another player an item from your inventory. Example: /give PCGamesN minecraft:planks 13 1. This would give PCGamesN 13 Spruce Wood Planks. This command is much simpler when giving single objects, but is useful for very specific trades.

Teleport

/tp [TargetPlayer]
Used to instantly transport yourself or another player to a specific location in the world. Using another player’s name in place of the coordinates will transport the target directly to said player’s location.

Kill

/kill
Kills your character, adding another player’s name will apply the command to them.

Weather

/weather
Allows you to choose the weather or your world. Options include: , and

Creative mode

/gamemode creative
Changes the gamemode to Creative mode, which allows player flight, unlimited resources and stops mobs attacking you.

Survival mode

/gamemode survival
Changes the gamemode to Survival mode, which means mobs will attack you and you’ll have to gather all resources the old-fashioned way.

Set time

/time set 1000
Sets the time to day. Replace “1000” with “0” for dawn, “6000” for midday, “12000” for dusk and “18000” for night.

Change difficulty to Peaceful

/difficulty peaceful
Changes difficulty to Peaceful mode. Replace “peaceful” with “easy”, “ normal”, or “hard” for more of a challenge.

How to find your world’s seed code

/seed
This will produce a code for your world, note it down so that you can load up an identical one in the future.

Keep inventory when you die

/gamerule keepInventory true
Ensures you don’t lose your items upon dying. To revert this, type “false” in place of “true”

Stop time

/gamerule doDaylightCycle false
This will stop the game’s day/light cycle in it’s place, allowing you to live under permanent sunshine or moonlight. To resume the day/light cycle type in “/gamerule doDaylightCycle true”.

Summon

/summon
Instantly drops a desired creature or object into your world, especially handy for when you’re short a couple of tame ocelots.

Cannon

/cannon
Shoots a TNT block at where the player’s pointing.

Atlantis mode

/atlantis
Dramatically raises the world’s water level, submerging all but the highest mountains.

Jump

/jump
Teleports the player to where they’re facing

Mob damage

/mobdamage
Mobs can’t deal any damage to you.

Ride

/ride
Turns the creature you’re facing into a mount.

Instant mine

/instantmine
One-click mining with any tool.

Freeze

/freeze
Stops mobs in their tracks.

Fall damage

/falldamage
Turns fall damage on and off.

Freeze

/freeze
Stops mobs in their tracks.

Fire damage

/firedamage
Turns fire damage on and off.

Water damage

/waterdamage
Turns water damage on and off.

Smelt item

/superheat
Turns all items into their smelted form.

Instant plant

/instantplant
No more waiting around for a planted seed to grow.

Store items

/dropstore
Stores all inventory items into a chest, which spawns nearby.

Item damage

/itemdamage
Weapons no longer receive damage or degrade.

Duplicate

/duplicate
Copies and drops the item stack that you have equipped.

Those are all the basic commands, but if there's something more specific you're looking to do with console commands check out a more thourough guide here: https://minecraft.gamepedia.com/Commands