Rechargeable nickel metal hydride batteries come in two types - regular NiMH and low-discharge NiMH. Regular NiMH has the higher milliamp but loses a bit of charge every day that the battery is off the charger whereas low discharge NiMH is a bit lower in milliamp but will hold a charge when not in use for many months.
Not sure which is best for your device? A good way to decide which would be best for your application is to consider how much use it will get. If you will be using the device weekly or more frequently and it is a high drain item ( think digital cameras, camcorders and radios ), go with the higher milliamp regular discharge batteries and get the most run time per charge. If your application is low drain ( think remote controls and such ) or a high drain that you use infrequently, get low discharge batteries and know that the lower milliamp will be compensated for by the fact that the batteries will be ready when you need them.
Remember - no special charger is required for low discharge NiMH. Any charger that handles NiMH will charge low discharge NiMH.