6DOF constraint is generic constraint can emulate a variety of constraints, by configuring each of the 6 degrees of freedom(dof).

Icon Size:
Defines size of the icon in the viewport.

Master Object:
Master object is base object of constraint. You can pick Dynamic / Static / Kinetic object for this. If you don’t use this option, objects constraint to this icon position.

Disable Collision:
When checked, disable collision between master object and constraint object.

Constraint Object:
You have to pick Dynamic Object for this.

Pick:
Select single object to add from viewport.

Add:
Select multiple objects to add from scene explorer.

Remove:
Remove selected objects from the list.

Linear:
Limit: X: Y: Z:

When checked, distance limits are enabled for each axis.

Low:
Defines the lower distance limit.

High:
Defines the higher distance limit.

Angular:
Limit: X: Y: Z:
When checked, rotation limits are enabled for each axis.

Low:
Defines the lower rotation limit.

High:
Defines the higher rotation limit.

Breakable:
When checked, constraint breaks when objects get some impulse.

Impulse:
Defines breakable impulse threshold. If object get impulse larger than this, constraint breaks.

Motor:
Linear X: Y: Z:
When checked, linear motor are enabled for each axis.

Velocity:
Defines the amount of velocity along moving axis.

MaxImpulse:
Defines the maximum allowed impulse.

Angular X: Y: Z:
When checked, angular motor are enabled for each axis.

Velocity:
Defines the amount of velocity along joint axis.

MaxImpulse:
Defines the maximum allowed impulse.

Spling:
Linear X: Y: Z:
When checked, spring when reached to the linear limit are enabled for each axis.

Softness:
Defines bounciness or springiness of the slide distance limit.

Damping:
Defines dampening force for the slide distance limit.

Angular X: Y: Z:
When checked, spring when reached to the angular limit are enabled for each axis.

Softness:
Defines springiness of the angular limit.

Damping:
Defines dampening force for the angular limit.