Working class – these are the people whose main source of income is a salary, be they doctors, janitors or software engineers. You can own stock and get dividends from it, you can own a second or third hous that you rent out, you can own your own small business, it doesn't matter. If you can't put food on the table without a job, you're working class.
Owner class – these are the big investors, big landlords, corporate CEO's and so on. Sure, some of them technically have a job (managing proprieties or running a company), but if the majority of their income (let's say 70%) comes from rents or investments or company bonuses, then they are owning class.
The reason this distinction is important is because it separates people based on their interests. Workers want higher wages (so they can have more money), owners want lower wages (so then products can be made cheaper, resulting in higher profit margins), workers want lower costs of living (so their money can buy more things), owners want higher costs of living (as higher rents and product prices lead to higher profits).
The more people understand this basic distinction the better chance we have at addressing the issues that plague us. First step is identifying and acknowledging the problem.
The majority of this post must be credited to fellow Redditor u/cristiander