Carol, please don't feel bad about not understanding. Confusion is common wih all the changes PC has gone through with the 890 series routers. I suggest you install your motor in both bases and be sure they sit level and do not rock. Among the many problems encountered with this series of routers was the screws that hold the height adjusting rack to the motor housing shearing off, motors that were prone to catching fire, both the plunge base and fixed base had so many defective castings that PC scrapped both bases and designed new ones. The really sad part of this was maybe 40% of the routers were to specs and worked fine. So far everyone has been satisfied with the latest crop of 890 routers; PC did get it right in the end and they do offer free replacement base's (exchange) for the defective units that slipped through.
"Living in the D" (this means Detroit!)
"It's fine to disagree with other members as long as you respect their opinions"