- the difference in height between the heel part and the toe part is zero (zero heel to toe drop). like how high heels are bad cuz they tilt you forward messing with your posture
- space for your toes via a wide toe box. over time your toes can even spread out more giving you more stability etc but you have to give your toes the space to do that!
- shoe is well connected to your foot. eg flip flops that flap when you walk are not great. traditional birks are not great either, sandals with heel straps are better. shoes are great.
- flexible sole, so your feet can bend and grasp the ground as appropriate. this makes me think of monkeys. this also helps u develop more of an arch over time
internet doesnt have consensus on whether you should use barefoot shoes in all contexts eg lots of walking on concrete.
but barefoot shoes are known to increase foot strength and stability like barefoot running drills do (theres a study!), and also improve technique. so personally im going to buy some and wear them at least some of the time