The IPlayer interface allows you to view certain information on a specific player and interact with said one. Mostly used in Event Handlers and Recipe Functions.

It might be required for you to import the package if you encounter any issues (like casting an Array), so better be safe than sorry and add the import.
import crafttweaker.player.IPlayer;

IPlayer extends IEntityLivingBase. That means all functions available to IEntityLivingBase Objects also are available to IPlayer Objects.
IPlayer also extends IUser. That means all functions available to IUser Objects also are available to IPlayer Objects.

Zengetters are for retrieving information. Usually either assigned to a variable or used in a method/function.

Zengetter	功能	返回值类型	Usage
Zengetter uuid	功能 返回玩家UID	返回值类型 string	Usage 播放器.uuid
Zengetter name（名称）	功能 returns the player's name	返回值类型 string	Usage player.name
Zengetter data	功能 returns the player's data	返回值类型 IData #数据	Usage player.data
Zengetter xp (经验值)	功能 returns the player's experience level. Can also be used to set a player's experience level	返回值类型 int	Usage player.xp
Zengetter hotbarSize	功能 returns the player's hotbar size	返回值类型 int	Usage player.hotbarSize
Zengetter inventorySize	功能 returns the player's inventory size	返回值类型 int	Usage player.inventorySize
Zengetter currentItem	功能 returns the item the player is currently holding	返回值类型 IItemstack	Usage player.currentItem
Zengetter creative	功能 returns if the player is currently in creative mode (a.k.a gamemode 1)	返回值类型 bool	Usage player.creative
Zengetter adventure	功能 returns if the player is currently in adventure mode (a.k.a gamemode 2)	返回值类型 bool	Usage player.adventure
Zengetter x	功能 returns the player's current X position in the world	返回值类型 double	Usage player.x
Zengetter y	功能 returns the player's current y position in the world	返回值类型 double	Usage player.y
Zengetter z	功能 returns the player's current z position in the world	返回值类型 double	Usage player.z
Zengetter position	功能 returns the player's current position. Can also be used to set a player's position	返回值类型 Position3f	Usage player.position
Zengetter foodStats	功能 returns the player's foodstats.	返回值类型 IFoodStats	Usage player.foodStats
Zengetter bedLocation	功能 returns the location of the player's bed.	返回值类型 IBlockPos	Usage player.bedLocation
Zengetter fishHook	功能 returns the player's fishingrod entity.	返回值类型 [IEntityFishHook ](/Vanilla/Entities/IEntityFishHook /)	Usage player.fishHook
Zengetter foodStats	功能 returns the player's foodstats.	返回值类型 IFoodStats	Usage player.foodStats

ZenMethods 是为了与其他东西做事，在这种情况下是与一名玩家做事。

ZenMethod	Parameter Type(s)	功能	例子
ZenMethod removeXP(XPtoRemove)	Parameter Type(s) int	功能 Removes the given experience levels from the player.	例子 player.removeXP(1)
ZenMethod update(IData)	Parameter Type(s) IData #数据	功能 Updates the playerdata to the provided IData.	例子 ​
ZenMethod sendChat(Message)	Parameter Type(s) string OR IChatMessage	功能 Sends the player a Chat Message.	例子 player.sendChat("Hello my old friend")
ZenMethod sendStatusMessage(message, hotbar)	Parameter Type(s) string OR IFormattedText	功能 Sends the player a status message, if the hotbar argument is true, the message will be displayed on player's hotbar, the default value is true	例子 player.sendStatusMessage("hello, world")
ZenMethod sendRichTextStatusMessage(message, hotbar)	Parameter Type(s) ITextComponent	功能 same as sendStatusMessage, but the message is an ITextComponent	例子 ​
ZenMethod getHotbarStack(index)	Parameter Type(s) int	功能 Returns the item at the given index within the player's hotbar.	例子 player.getHotbarStack(3)
ZenMethod getInventoryStack(index)	Parameter Type(s) int	功能 Returns the item at the given index within the player's inventory.	例子 player.getInventoryStack(3)
ZenMethod give(item)	Parameter Type(s) IItemstack	功能 Give the player the provided item. Item is an IItemStack.	例子 player.give(<minecraft:gold_ingot>)
ZenMethod teleport(position)	Parameter Type(s) Position3f	功能 Teleports the player to the provided position in the same dimension	例子 player.teleport(position)
ZenMethod executeCommand(raw)	Parameter Type(s) string	功能 Executes the command as the player	例子 player.executeCommand("kill")
ZenMethod dropItem(dropAll)	Parameter Type(s) bool	功能 Drops the current item (or the entire stack) that the player is holding.	例子 player.dropItem(false)
ZenMethod dropItem(itemToDrop)	Parameter Type(s) IItemstack	功能 Drops the provided item at the player's position.	例子 player.dropItem(<minecraft:dirt>)
ZenMethod getCooldown(item)	Parameter Type(s) IItemstack	功能 Gets current cooldown of specific item for the player	例子 player.getCooldown(<minecraft:ender_pearl>)
ZenMethod setCooldown(item, time)	Parameter Type(s) IItemStack, int	功能 Sets cooldown time of specific item for the player	例子 player.setCooldown(<minecraft:ender_pearl>, 3)