The youth programs and shows are included in your cruise fare. Food in the Windjammer buffet and main dining room is also included, plus room service food and, depending on the ship, you also have other 'free' food choices such as Sorrento's pizza and Cafe Promenade. If the ship has a Hot Dog Haus (they are adding them to older ships after it was a hit on the Allure Of The Seas), then it is included as well. Note that room service orders between midnight and 5am do have a $3.95 delivery fee. Also, at any time of the day or evening, if you order room service it is proper to give the deliverer a couple bucks tip.
Extra-fee dining includes Johnny Rockets, Chops, Portofino, Giovanni's Table, and other venues that depend on the ship. Some ships have more than the others.
Gratuities for your dining and cabin staff are extra, as are all bar purchases which includes soda too.
It is a very good idea to use a cruise-specialist travel agent to book a first cruise. They can explain everything to you before you book. Too many people decide to do it themselves on-line, and then they get surprised by some things when they board the ship, and they then let those surprises ruin their cruise.