A server is a process which implements the dm_env_rpc Environment gRPC
service. A server can host one or more worlds and allow one or more client
connections.
A client connects to a server. It can request worlds to be created and join them to become agents. It can also query properties and reset worlds without being an agent.
A client which has joined a world. In a game sense this is a "player". It has the ability to send actions and receive observations. This could be a human or a reinforcement learning agent.
A system or simulation in which one or more agents interact.
An agent's view of a world. In limited information situations, the environment may expose only part of the world state to an agent that corresponds to information that agent is allowed by the simulation to have. Agents communicate directly with an environment, and the environment communicates with the world to synchronize with it.
A series of discrete states, where one state is correlated to previous and subsequent states, possibly ending in a terminal state, and usually modified by agent actions. In the simplest case, playing an entire game until one player is declared the winner is one sequence. Also sometimes called an "episode" in reinforcement learning contexts.