What are environment variables?

Environment variables are dynamic values that impact the behavior of running processes and applications on a computer system. They provide a way to influence how programs execute without requiring changes to the code. For instance, environment variables can define paths to executable files, specify system language preferences, or configure user settings for various applications. Because these variables can be changed while the system is running, they allow flexibility in application management and configuration.

In contrast, the other options do not accurately reflect the characteristics of environment variables. Fixed values set during the installation of applications relate more to configuration settings rather than the adaptive nature of environment variables. Static configurations imply unchanged settings, which contradicts the very idea of environment variables being modifiable at runtime. Lastly, while a system administrator can modify environment variables, this does not encompass the broader usage where any user may manage their personal environment variables without administrative privileges. Thus, the dynamic nature of environment variables is what makes the second choice the most accurate description.