The FASL variables at the top are used to identify the parameters used to determine when the check is run against a target system. So in your example above, that check is identified as...
- Non-intrusive check
- Requests a TCP connection to the target device
- Runs only against systems with a major category of Linux
- Filters the potential scope of systems based on a Regex os filter, meaning the OS name must contain any of the osVersion information
Per your second question, it is my understanding that parms is just a variable to allow you to pass a variable between different functions.