Those scary terms are actually dead simple


ISP = Internet Service Provider

VPN = Virtual Private Network — more info

Adversary = an attacker; a threat to your privacy and/or security endeavors

Cryptography = the practice and study of techniques for secure communication in the presence of third parties called adversaries — more info

Threat model = a model of the most probable threats to your security/privacy endeavors. — more info

Message = any data in the context of cryptography; usually data that is to be encrypted — more info