This tool creates a frame out of any other moving frame. These frames are meant to be used in situations where you want to specify a motion relative to a the position of a robot's body part at a time in the past.
For example, you might want to record a generic pulling behavior that pulls for 15 cm starting at the left gripper's current position. In this case, you would create a Freeze Frame action for l_gripper_tool_frame then create either a Velocity Priority or Position Priority node that pulls for 15 cm using the frozen frame as a reference point. If you attempted this using the l_gripper_tool_frame as a reference point it would not work as the l_gripper_tool_frame itself would be continuously moving!