Enchantment Books: When looking at an enchantment book in your inventory a description of the enchantment is added to the tooltip. This only happens if the player is in advanced mode. Advanced mode is a vanilla feature in Minecraft that is enabled by hitting ctrl + f3 and h on the keyboard. Only a description for the first enchantment on an enchantment book will be given.
Entity Equipment: If you look at a mob that is holding a piece of armor or an item, the item will be noted in the tooltip. This shows the display name of the item, meaning it is possible for the name shown to be renamed.
Furnaces: When looking at a furnace that is currently smelting, the remaining duration of the fuel will be printed in the tooltip. When sneaking information such as the item being in the input, output and fuel slots, along with how much of each is in the stack.
Block Harvest Module: When looking at a block the harvestability of that block is calculated and depending on the result certain bits of information will be added to the waila HUD. If the current item in your hand is not the suggested tool to use the correct tool type will be added to the hud. If it is the correct tool then the tier of the block and the held item are then compared, the hud will then indicate if the tool is a high enough tier.
Horses: When looking at a vanilla horse its jump stat and speed stat will be represented on the Waila HUD. This information can be used to compare two horses or to potentially breed better horses.
Item Frames: When looking at an item frame the name of the held item is added to the Waila HUD. This uses the display name of the item so it is possible to change the name shown by renaming the item.
Pets: When looking at a tamable mob the name of the owner is displayed in the Waila HUD. This uses the nbt of the entity to generate the owner name. The keys used include Owner, OwnerName, owner and ownerName it is also possible for mods to add their own keys to this list by using IMC.
Player Heads: When looking at a player head, the name of the head owner is added to the Waila HUD.
Configuration: Almost all aspects of this mod can be disabled using the in game Waila Configuration. This configuration can be accessed normally through the Numpdad0 key however it is possible to change this in the controls section. When joining a server with this mod installed the server will have the ability to override your config options.
Additional Mod Support:
Pixelmon: When Pixelmon 3.2.2 or newer additional information will be supplied for Pixelmon. When looking at a Pixelmon and sneaking information such as nature, ability, happiness, held item and size will be added to the Waila HUD. When looking at an Apricorn Tree information such as the growth rate and apricorn type are added to the Waila HUD.