Old tech is brushed motors, new tech is brushless motors. Can handle more power plus nearly maintenance free.
Battery wise you had NiMh and NiCd and new guy is LiPo. Same as laptops and mobile phones I think. Have longer runtimes plus pump out higher voltages for their size compared to the stick packs. Just need a bit of special treatment with charging and making sure they stay within a set voltage range. (YouTube lipo accidents). But if you don't abuse them then perfectly safe.