Is the database on the same server as the poller generally and how would I be able to find out if it is?
SolarWinds best practices recommend against installing SQL and Orion on the same machine, though in smaller environments this may be less of an issue. You can find information on the SQL Server and database Orion is using by going to [Settings -> Database Details]
If they are seperate can you add a poller to the network and use the same database or not?
Yes. All Orion Additional Pollers write to the same SQL database as the primary Orion server.