I wondered the same, after some Google’ing I found this:
IS_SRVROLEMEMBER (Transact-SQL) indicates whether a SQL Server login is a member of the specified server role.
I figure that a good understanding of SQL, TSQL & general Database administration is needed to “know” that this is the right command to use.
And for those that don’t “know”… we use Google lol
(For example; if you search “How do I identify all super users in SQL Server?”
IS_SRVROLEMEMBER is mentioned a lot!!)
Hope this helps??