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units/en/unit2/glossary.mdx

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-# Glossary
+# Glossary [[glossary]]
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+This is a community-created glossary. Contributions are welcomed!
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 ### Strategies to find the optimal policy
 
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 - **The state-value function.** For each state, the state-value function is the expected return if the agent starts in that state and follows the policy until the end.
 - **The action-value function.** In contrast to the state-value function, the action-value calculates for each state and action pair the expected return if the agent starts in that state and takes an action. Then it follows the policy forever after.
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+If you want to improve the course, you can [open a Pull Request.](https://github.com/huggingface/deep-rl-class/pulls)
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+This glossary was made possible thanks to:
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+- [Ramón Rueda](https://github.com/ramon-rd)