Sets a GameObject's position, rotation and/or scale to match a Target in world-space.

This GameObject's parent hierarchy no longer contributes its positioning in space when one of these options is turned on. For example, if you constrain the position of an object to another object, it will still rotate with its parent but it will 'stick' to the other object's position.

This constraint is the corner-stone of animation setup/rigging and can be used to create simple behaviors or combined in creative ways to make more complex behaviors. Generally this type of constraint is only used when changing an object's parent is either not possible, or would break a hierarchy, or, most commonly as part of a more complex setup. This is a big subject with numerous applications. You can read a few examples on this documentation's home page.

Target

The object to reference for position, rotation and/or scale.

Mode

(See main documentation page)

No Target Mode

(See main documentation page)

Position

Place this GameObject at the exact world-space position of the Target.

Rotation

Set the rotation of this GameObject to the exact world-space orientation of the Target.

Scale

Set the scale of this GameObject to match the world-space scale of the Target.

Scale is rarely needed and is a little more computationally expensive than position and rotation, which are actually very light and quite simple to perform. For this reason, do not turn on scale unless you need it.

This only matches the center/pivot of the Target and may not take complex hierarchical  rotations in to account. This means that, depending on the hierarchy of the Target, even if both objects have the same mesh and scale, they may not match visually if parent rotations are causing geometry shearing (distorted space).

Generally it is a bad idea to use scaling, especially in combination with rotations, but there are times where it is needed. Usually a uniform scale will work fine though.