Is a background process a Session in Oracle. Is it that say DBWR has 1 session, LGWR has 1 etc...

I'm quite confused with this.

-- What I think ??

Oracle in order to manipulate dictionary needs its own session(s). Each session in turn will obtain RBS, TEMP, generate Redo just like a regular session all to manipulate the Data Dictionany.

But again why more that 1 session ??