Battery Charger :D

It means it is a slow charger for NiMh (old type) batteries. That means it charges for over half a day, but does not damage the battery in the long run (and won't set your house on fire either).

you cant charge any batteries with a charger.
the specifically need to be "rechargable"

that will work good enough but that sounds like a VERY old and "dumb" recharger.
if you need the batteries for anything semi-serious like lights on your bike you should really consider getting a new smarter charger.

smart chargers don't overcharge batteries, they don't charge damaged / defective batteries and they charge way faster (x5 or even x10 if you are in a hurry). also they pause charging when the batteries get too hot and generally minimize the impact on your batteries' lifespan since the recharge cycles for any battery are limited.
or short: they are way superior to your old charger and your batteries will thank you.
with a good charger you can get a lot out of even cheap batteries from the local supermarket.
a bad charger will ruin even the best batteries in a hurry.

Output: AA-2x 1,4VDC 140mA and AAA-2x 1,4VDC 80mA

That is the charging current not the overall capacity. The lower the number, the longer it takes to charge it but the safer it is in the long run. The higher the number, the less time it takes to charge it but the higher the chances to shorten the accumulator's lifespan. The accumulator's capacity is measured in Ah (ampere hour) or mAh (milliampere hour).

In other words you can use a slower charger to charge a bigger accumulator as long as it can withstand the extended running time. It'll just take way longer than with faster chargers. Also make sure you're using the proper type of charger according to the accumulator's chemistry (e.g. NiMH, NiCd, Li-Ion, Li-Po).