What is the stock market?

i'm not 18 yet, but i'm just planning ahead. exactly what is the stock market? is it a bunch of products and companies and their ups and downs. how do you profit from it. can i get a simple example like dogs sell better than cats so yada yada yada..something simple so i get the gist because i don't think i'll understand the technical terms otherwise. how do you gain the most profit from the stock market? are there any strategies?