What are mission critical technologies?

Could you please elaborate on what mission critical technologies entail? Are they simply the most important technologies for a business's operations, or do they encompass a broader range of functionalities? How do companies identify which technologies are mission critical, and what measures do they take to ensure their reliability and resilience in the face of potential disruptions? Furthermore, what are some examples of mission critical technologies commonly used in the finance and cryptocurrency sectors, and how do they contribute to the overall success and stability of these industries?