We don't know much about this except for what's been said in the patch notes today.
Following features and functions will be added to free company.
During phase 4, only characters carried over from Version 1.0 above level 25 can form a free company.
By forming a free company, players will gain access to a company chest, which can be used to share items between free company members. In addition, members can accrue free company experience points and free company credits.
Accruing free company experience points will unlock the following features:
By speaking with the OIC officer of arms in any of the three cities, players can create a company crest.
The maximum capacity of the company chest will increase.
By speaking with the OIC officer of arms in any of the three cities, players can affix their company crest to gear.
Free company actions will become available
The following actions can be purchased from OIC quartermasters using company credits:
The Heat of Battle - Increases EXP earned through battle
Earth and Water - Increases EXP earned through gathering.
Helping Hand - Increases EXP earned through crafting.
A Man's Best Friend - Increases EXP earned by companions.
Brave New World - Increases the attributes of all members under level 10.
Live off the Land - Increases Gathering.
Eat from the Hand - Increases Craftsmanship.
What You See - Increases Perception.
In Control - Increases Control.
That Which Binds Us - Increases spiritbonding speed.
Meat and Mead - Increases duration of food effects.
Proper Care - Slows gear wear.
Back on Your Feet - Reduces the duration of Weakness.
Reduced Rates - Reduces teleportation fees.
*Because chocobo companions are not available during phase 4, A Man's Best Friend will have no effect.
Purchased actions can be accessed under Actions in the Free Company menu.