What is the relationship between transmission of information and group velocity of a wave packet? I always keep hearing things like information always travels at the group velocity, it can't go faster than light etc. While I do understand (to an extent) about information not exceeding the speed of light, my question is, why does it have to propagate only at the group velocity? What does information even mean in this context? Lastly, why does information travel in the form of a localized wave packet? Is it because plane waves are infinite in extent but information isn't? Sorry for asking too many questions, but I think all of them are interrelated in some way. I am not having a good time making sense of this. Any help would be appreciated. Thanks a lot !!