Joseph Beggy

Hi I play guitar. Generally all styles.
My oldest is a Suzuki G-150 nylon string Spanish guitar that I bought in 1974!! Also a yamaha CPX15 steel string acoustic. A 1993 strat delux and an ibanez 103 AS. The AS has an 335 style.
I stumbled on this site while looking for the music of Brian Finnegan the Stars. I noticed what appeared to be a form of notation reading d2f2/ g2??? I’m puzzled with this. Can you explain!!