Hi,
Ok, let´s begin:
In the past , starting in the 1980s, Playmobil bought the tracks at LGB. These tracks were made on brass and there connected, like a HO-railway, to a transformer. So the engine in the loco is powered via the track.
In the mid of 1990s Playmobil decided to use plastic tracks. At this point each loco needs a battery pack to power the engine and the RC receiver. The loco is now controlled via radio control.
A RC-loco can be used on both track types, but the older trains can not be used on plastic tracks as plastic do not leads current.
About compatibility: LGB-tracks are compatible to LGB and plastic tracks are compatible to plastics...... and not vice versa.... In the past DS has offered an adapter which allows to combine both track versions, but this is sold out since ages.
Regards
Rainer
BTW: Do not start with trains. This is a cureless virus....