The xpTransform modifier causes the particle's position, scale or rotation to change in conformity with another object.

What this means is that if the linked object moves (for example) by +100 units on the Y-axis, the particles will also move +100 units on the Y-axis from their current position.

Object Properties

xpTransform Object tab menu.

Enabled

Checking this box enables the xpTransform modifier.

Mode

Set at Independent by default.

You can change this to Action-Controlled.

Independent Mode

In this mode, particles will be affected if they come into the field of effect of the modifier.

Action-Controlled Mode

When in the Action-Controlled Mode setting, the modifier will only act on a particle when told to do so by an action.

Object

Drag the object to be linked to the particles into this field.

If the field is empty, the modifier will have no effect.