Newbie question

So there is gonna be a local chess tournament where I live and the description says:

"5SS, G/150, except for RD. 1, which is G/75."

I'd really appreciate if someone could explain what it means.

5 round Swiss System.  Time control is game in 150 minutes except for round 1 which is game in 75 minutes.

Swiss system is a type of pairing system where, by my understanding at least, players are ranked by rating and the list is cut in half and the top player on the first list is paired with the top of the 2nd list etc.  Often this means your first round is against someone either much better or worse than you :)  But after that player are paired to match their wins and draws, so each round you get a closer match (ideally anyway) and the last round the two players with the most wins and draws get to play each other.

Swiss is the most common type of tourney you'll see.  World class, or otherwise exclusive, events use RR which is round robin (every participant plays every other participant) or double round robin where each participant plays everyone else as black and as white.  As you might imagine this could take quite a long time if there are more than a few players.

Game in 150 means each player gets 150 minutes on their clock.  So a game could conceivably last for 300 minutes (5 hours).

SS : In this case means swiss system a tournament format where players are paired based on rating and score (easier to look up online than explain here)

RD 1 : RD =  Round

G/75 : Game/ (time control in minutes) so game in 150 minutes except the first round which is 75 minutes

the only question I would have is that if there is an increment or not. some times they dont list it since its expected other times they dont. depends. usually default is if its not listed then there is no increment

I see, thank you guys very much for the information!