This document has everything you need to know about MCMMO and it's MANY perks and features.

Parties:
Parties in MCMMO is how you unlock extra XP & perks, below is a list of commands that are essential for maximum potential of the party feature

/Party Create (PartyName) (Password - Optional)
/Party Join / Accept (Password if there is one)
/Party Invite (Player)
/Party Alliance (Party)
/Party Itemshare
/Party XPShare

Creating parties has it's benefits and rewards, being in a party and ranking up together you will rank up your party and at different levels you will obtain perks,
At Levels:
1 - Party Chat
10 - Party Teleport
25 - Alliances
50 - ItemShare
100 - XPShare

Party Chat - Party chat is just a basic chat you can use to communicate to other party members.

Party Teleport - Another simple reward you will be able to teleport to other party members

Alliances - You can create an allicance with another party, this will make your party and another party "Friends" you will not be able to damage any player that is in either party, this will be useful when it comes to PvP events where you need to be careful on who you are hitting

ItemShare - Itemsharing is a perk that allows party members within a 50 block radius to share items evently, This means if you mine 6 diamonds and you're near 1 party member you will get 3 and your party member will also get 3.

XP Share - This is probably one of the best features and will allow you to gain MCMMO levels much faster! XP Sharing is done by location, if you are within 150 blocks of a party member you will both get MCMMO XP, If you mine an ore and you have 1 player within 150 blocks you will get the full XP and the other playe will get 10% bonus xp for doing nothing. The different tiers of XP are as follows:

1 Player - 10% Bonus XP
2 Players - 15% Bonus XP
3 Players - 20% Bonus XP
9 Players - 45% Bonus XP
10 Players + - 50% Bonus XP

Skills:
There are many skills that need leveling up and give you perks & abilities as you rank up, below is a list of all the skills and how to level them up and what rewards you get:

Taming:
How to level up: Taming Horses & Ocelots
Unlocking Abilities: Environmentally Aware (Lvl 100) - Gore (Lvl 150) - Pummel (Lvl 200) - Fast Food Service (Lvl 200) Thick Fur (Lvl 250) Holy Hound (Lvl 350) - Shock Proof (Lvl 500) - Sharpened Claws (Lvl 750)

Mining:
How to level up: Mining blocks
Unlocking Abilities: Double Drops (Lvl 1) - Super Breaker (Lvl 50) - Blast Mining (Lvl 125) - Bigger Bombs (Lvl 375) - Demolitions Expertise (Lvl 500) 

Excavation:
How to level up: Digging Blocks
Unlocking Abilities: Giga Drill (Lvl 50) - Archaeology (Lvl 50)

Fishing:
How to level up: Fishing
Unlocking abilities: Treasure Hunting (Lvl 1) - Magic Hunter (Lvl 1) - Shake (Lvl 1) - Fishermans Diet (Lvl 1) - Master Angler (Lvl 125)

Acrobatics:
How to level up: Fall Damage
Unlocking Abilities: Roll (Lvl 1) - Dodge (Lvl 1) Graceful Landing (Lvl 1)

Woodcutting:
How to level up: Cutting down trees
Unlocking Abilities: Harvest Lumber (Lvl 1) - Tree Feller (Lvl 5) - Leaf Blower (Lvl 15)

Swords:
How to level up: Hitting any mob or player with your sword
Unlocking Abilities: Serrated Strikes (Lvl 1) - Rupture (Lvl 1) - Counter Attack (Lvl 1)

Unarmed:
How to level up: Punching players or mobs
Unlocking Abilities: Beserker (Lvl 1) - Steel Arm Style (Lvl 1) - Arrow Deflect (Lvl 1) - Disarm (Lvl 1) - Iron Grip (Lvl 1)

Herbalism:
How to level up: Harvesting Plants & Crops
Unlocking Abilities: Double Drops (Lvl 1) - Hylian Luck (Lvl 1) - Farmerss Diet (Lvl 1) - Shroom Thumb (Lvl 1) - Green Thumb (Lvl 1) - Green Tera (Lvl 50)

Axes:
How to level up: Hitting any mob or player with an axe
Unlocking Abilities: Skull Splitter (Lvl 1) - Critical Strike (Lvl 1) - Axe Mastery (Lvl 1) - Armour Impact (Lvl 1) - Greater Impact (Lvl 1)

Repair:
How to level up: Right click damaged armour & tools on an iron block or gold block (Iron to repair & gold to salvage)
Unlocking Abilities: Arcane Forging (Lvl 125) 

Archery:
How to level up: Shooting a player or mob with a bow and arrow.
Unlocking Abilities: Arrow Retrieval (Lvl 1) - Daze (Lvl 20) - Bonus Damage (Lvl 50)

Alchemy:
How to level up: Creating and modifying potions in a brewing stand
Unlocking Abilities: Catalysis (Lvl 100) - Concoctions (Lvl 100)