Can someone please tell me what the advantages/disadvantages would be with a stateroom on deck 1?

Not sure what you mean. Cabins usually start on decks higher than this, like 4 or 5. Lower decks are typically inside cabins or cabins with a window.

If you think you may be prone to motion sickness then you want low and middle. If not the cabins with balconies are usually higher up.

Jacketwatch is correct. There are decks below the passenger decks where crew members have their cabins (off limits to passengers).

When I started cruising, I would get a cabin on the lowest passenger deck (outside with a porthole). Nothing wrong with that deck other than the ocean seems really close from the porthole and water may splash on it in windy/rough weather.

Our first cruise was in slower deck cabin with a window. The first morning we woke up and thought we were in port. We looked the window and were amazed we were still at sea. It was that smooth.

On some ships that we have been on Deck 1 is the deck where the pursers office and excursion office are located, and also the dining room. Problem is thta there can be a good bit of traffic. Look at the deck plans for the ship you are considering. That may help you decide.

He might think Deck 1 is at the top of the ship??

I saw deck 1 offered on some ships, don't remember which cruise company. This is the lowest deck, so the motion is the smallest - this would be good for people with motion sickness BUT if you are in front, you can feel the motor vibration and the anchor being released - this is what I was told by people who were below us.

Deck 1 can be in alot of places. The last ship we were on Deck 1 was above decks A and B, but was the lowest passenger deck.

Generally the higher decks are more desirable. Choosing a cabin mid ship is convenient to lifts/stairs I prefer the Starboard side traveling north and port traveling south for viewing Try to avoid booking stateroom on decks with lots of public areas...such as theatres as the traffic and noisy travelers passing your stateroom especially late in the evening can be disturbing