Our economy is structured around the idea of private property. This doesn't mean your toothbrush, or your Playstation. Private property are goods used to make a profit: factory machines, offices, medical equipment, shipping boats, rental homes, etc. Even if you own your own home, it's not really property in the sense I mean if you're personally living in it. Property used in this way is also called "Means of Production".
If you don't own means of production, then your only alternative is to sell your labor time. This makes you a worker, or working-class. The vast majority of people fall into this category. You sell your labor time, and produce a good or service, which is sold for a profit by the person who owns the property. Crucially, whatever you produce during your labor time is relinquished to the owner, you have no claim to it.
The owners have disproportionate economic power in this arrangement. They have total control over wage paid to the worker, they have total control over the market price of the good produced by the worker. Furthermore, they can do whatever they want with the means of production itself. So they can close that factory, or change that shipping route, or buy newer equipment which requires fewer workers to operate.
Over time, this disproportionate economic power also manifests as political power. Politicians cater to the interests of the owners because they're dependent on them for campaign money. News outlets tend to articulate the preferences of the owners. Universities tend to promote professors who teach the preferred ideas of the owners, and so on.
This is a very simplified version, but hopefully you can see how our economy is structured to empower a tiny minority of people. I advocate for a system where the means of production are not owned by a small number of people. Instead, the workers would administer the means of production democratically on the basis of one worker, one vote. I think such a model would stop producing a tiny minority of people with disproportionate power in society.