Where is the dirty bit located?

Could you please clarify for me where exactly the "dirty bit" is situated? I'm having trouble pinpointing its location within the system or the context you're referring to. Is it a specific part of the blockchain, perhaps related to transaction validation or security measures? Or is it a term used in a different context altogether? It would be greatly appreciated if you could provide more detail or context to help me better understand where this "dirty bit" can be found.