Here’s the simplest way to define marketing
If you’re on the verge of completing a Zoo and you’ve set a date for the opening ceremony, you write something on a billboard that says “Zoo Coming Soon” that’s advertising.
If you get a monkey to jump around the entire city, go to special places like parks, malls, train stations, etc wearing a t-shirt “Zoo coming soon” that’s promotion.
If the Monkey steals some banana at the mall and gets arrested by the police, and the video goes viral on YouTube or Instagram, that’s publicity.
If you get the Monkey to make people in the mall excited and to laugh, that’s public relations.
If the people troop into the Zoo’s opening ceremony, and you get them to see the monkey that stole the banana now wearing a police uniform and take them around to see other animals and they get to participate in other fun games and activities within the Zoo, spend a lot of money, that’s sales
If you planned the entire lineup of events from the very beginning, that’s marketing.