If you’ve got enough money saved to fund, say, a chunk of a business; you can then find a bunch of other people to contribute the rest of the money you need. They’ll own a part of your business too; but you’ll have the cash you need to set things in motion. You get to launch your dream business. They get to be (and own) a part of it - #winning! This part they own is what the guys in suits call (drumroll): stocks.
A stock is the same thing as an equity or a share – other fancy words to describe the ownership you have in a business.