# What is Deep Reinforcement Learning? Definition & Technical Mechanics

> **Source:** [SPIDITS AI AI Glossary](https://spidits.com/ai-glossary)  
> **Category:** Model Training  
> **Canonical Citation:** [https://spidits.com/ai-glossary/deep-reinforcement-learning](https://spidits.com/ai-glossary/deep-reinforcement-learning)

## Definition
Deep Reinforcement Learning (DRL) is a subfield of machine learning that combines reinforcement learning principles (agents, actions, rewards) with deep neural networks to learn decision-making policies for high-dimensional state spaces.

## Architectural Mechanics & Deep Dive
Deep Reinforcement Learning (DRL) combines deep neural networks with reinforcement learning principles, enabling agents to learn optimal behaviors in complex, high-dimensional environments. The deep neural network acts as a function approximator, mapping states to actions (or values). This allows agents to solve complex decision-making problems—such as playing human-level Atari games, mastering Go, controlling robotic limbs, or optimizing energy grids—by learning purely from rewards.

## Industry Applications & Real-World Use Cases
Autonomous robotics navigation, game-playing systems (like AlphaGo), and complex financial trading.

## Frequently Asked Questions

### What role does the deep neural network play in DRL?
It acts as a function approximator, mapping high-dimensional inputs (like image pixels or sensor arrays) directly to action value probabilities.

### What is the difference between Q-learning and Deep Q-Networks (DQN)?
Q-learning stores state-action values in a static table, which fails for large spaces. DQN uses neural networks to predict those values.

## Related Terminology
- [reinforcement-learning](https://spidits.com/ai-glossary/reinforcement-learning)
- [rlhf](https://spidits.com/ai-glossary/rlhf)
- [deep-learning](https://spidits.com/ai-glossary/deep-learning)

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*From the SPIDITS AI Knowledge Base (336+ terms indexed). Explore full technical definitions: [https://spidits.com/ai-glossary](https://spidits.com/ai-glossary)*