1 Introduction  
2 OOD Detection and Related Areas  
3 Methodology  
3.1 OOD Data Available  
3.2 OOD Data Unavailable + ID Label Available  
3.3 OOD Data Unavailable + ID Label Unavailable  
4 Datasets and Applications  
5 Metrics  
6 Discussion  
6.1 Pros and Cons for Different Settings  
6.2 Large Language Models for OOD Detection  
6.3 Comparison between NLP and CV in OOD Detection  
6.4 Future Research Challenges  
7 Conclusion