What is game overlay?

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Tags

1. #customizable
2. #steam
3. #while
4. #interface
5. #access
6. #features
7. #differently
8. #incorporated
9. #depending
10. #steamworks
11. #overlay
12. #supports
13. #playing
14. #community
15. #because
16. #developer
17. #which
18. #games
19. #allows
20. #feature