No, it's not a charger, you can just only start the engine. Even with a dead battery.
And you can use it for your motorcycle as well, if it's using 12 Volt. Mine is working...
To charge the booster, you can either use the 12V Fast Charge port or the microUSB port. For fast charging, connect the Fast Charge cable to the booster and plug the other end into a 12V cigarette lighter socket in a vehicle. Alternatively, you can connect the microUSB port to a USB charger, but this will take longer. The charging LEDs light up slowly during the charging process.
The booster has its own built-in battery. However, its capacity is very limited. The capacity is 8 ampere hours. Normal car starter batteries have about 60 ampere hours. This means that this battery can supply 12/8 = 1.5 amps over one hour at 12V voltage (absolute ideal value). That is very little (8 watts) and hardly enough to run anything sensible. It can be used to charge a mobile phone or operate an LED lamp, for example. A camping fridge with 30 watts can be operated for a few minutes.
Basically, you can always connect directly to the battery, I always do it that way. Your Noco is also protected against polarity reversal, so as long as you don't press the (!) button for 3 seconds, you can't do anything wrong!
However, if the battery is not connected properly, your electronics in the vehicle could be damaged if you do not connect it to the body. Conversely, you would have had completely different problems... 😉