The NB-6LH and NB-6L batteries are both rechargeable lithium-ion batteries commonly used in Canon cameras. The primary difference is that the NB-6LH typically features enhanced performance with a higher capacity and better longevity compared to the NB-6L, allowing for longer shooting times. Additionally, the NB-6LH may have improved thermal management and safety features. However, they are interchangeable in devices designed for either battery type.