1 Introduction  
2 Definitions  
2.1 Large Language Models  
2.2 Training Stages of Large Language Models  
2.3 Hallucinations in Large Language Models  
3 Hallucination Causes  
3.1 Hallucination from Data  
3.2 Hallucination from Training  
3.3 Hallucination from Inference  
4 Hallucination Detection and Benchmarks  
4.1 Hallucination Detection  
4.2 Benchmarks  
5 Hallucination Mitigation  
5.1 Mitigating Data-related Hallucinations  
5.2 Mitigating Training-related Hallucination  
5.3 Mitigating Inference-related Hallucination  
6 Challenges and Open Questions  
6.1 Challenges in LLM Hallucination  
6.2 Open Questions in LLM Hallucination  
7 Conclusion