yes, these terms are not easy to understand and rarely well explained forward secrecy literally means that you can encrypt a message in a way that could not be predicted by an adversary usually such schemes involve using a seed value to derive a hash based on some temporal value, usually the time alone is sufficient it's my firm opinion that the field of cryptography and signals security have a long way to go in building adequate models to make this understanding accessible too many engineers, not enough teachers (i'm probably more teacher than engineer)

also, i appreciate this point: post compromise security is irrelevant in a system with persistent identities, only forward security matters