Passive USB - the devices automatically lock to each other without needing any additional equipment
Active - Acts as a USB hub and buffers all downstream and upstream data traffic. Both the low-speed, full-speed and high-speed USB devices will function equally well with the USB Extension Cable.
Main difference? You'll find that passive cables can only send signals up to around 16ft (around 5 meters). You can mix and match the cables without any problems. Where active come in handy is when you want to run more than 16ft.
You can do this:
16ft Passive => 16ft Active => 16ft Passive
Why? Beats me, if I were going that far I would just use all Active to ensure the best data transmission.
Using it in the car and going less than 16ft total just use a 10ft Passive OR a 16ft Passive.
From their excerpt it seems like they are talking about having a 6ft (passive) USB cable already hooked up to your printer and then using this extension to it. Similar to the diagram but in reverse, you would want the active at the device to "buffer" the first part and then the passive at the PC for transmission.
What exactly is your plan of attack? In my car I used a passive cable from the PC out to a HUB under my seat. The hub acts as a Active device so no need for an active cable. From there I used the HUB to plugin a DVD Rom, GPS mouse, and the touchscreen.
Based on the diagram I showed you we have PC => Passive => HUB (Active) => Passive (to device)