These lights are great for being seen on the road! I wouldn't recommend them for being able to see much though, as they aren't the brightest lights out there. What's nice about them is that they're lightweight, easily rechargeable, and the velcro straps make it so that they can be switched between different bikes at a moment's notice!
The package comes with only one USB charger, but luckily these lights charge relatively quickly so I don't think you really need to buy a separate charger. One should do the job! Charging is pretty easy, just make sure the magnets snap together and the light flashes periodically to know that the electrons are flowing to your device.
The front light has three modes: Steady, Overdrive, and Flash. The overdrive mode is a little bit brighter than the steady mode. The flashing mode makes me feel like I'm going to have a seizure, but it does save on battery and still allows you to be seen by other vehicles. But since these things are rechargeable, I just go with the steady mode.
The rear light similarly has three modes: Steady, Flash, and "Chase". Chase mode means that the 4 LEDs blink in an artsy back-and-forth pattern, which saves some batteries and can draw attention to you on the road.
I think these lights are great for people who want something that is very lightweight, small, rechargeable, and allows you to be seen by other cars. If you're looking for lights that can turn night into day, these might not be for you.