As a general rule, direct traders (such as the main FOREX participants) are either wealthy or acting as agents/brokers for many smaller investors. Or sometimes both.
Stocks can be traded in a number of ways. You can always buy from someone you know, assuming that they wish to sell (and are not prevented from doing so in the case of closely-held corporations). Then there are the over-the-counter networks, where my agent deals with your agent. Major trading in generally done via exchanges, since they provide better mechanisms and regulation of trading and in turn are usually licensed to do so by some government.. In olden days, people would typically have a specific person that they would use as their broker and the broker would often belong to a brokerage house. With the advent of the Internet, impersonal brokerages grew up such as fidelity.com and more recently, robinhood where it's strictly between you and your computers. The advantage of old-time brokerages was that they'd typically publish investment newsletters - although that practice I think has largely been abandoned nowadays. And the broker knew you and could tailor investment advice based on your needs and goals - subject to whatever products their employers were pushing, of course.
You can buy and sell currency at many banks as well as other locations. At one time, two staples at airports (back when you could board a plane and remain fully-clothed) were the carousel where you could pick up travel insurance and the booth where you could exchange currency. I think that both are now history. Travel insurance is often a perk with whatever credit card you paid for your tickets on and who needs hard cash when your credit card - or more recently, your cellphone's NFT app - can do direct transfers?
But those are generally pretty petty transactions. FOREX is an OTC system. One of its primary uses is to aid in international transaction systems such as SWIFT. Used as a vehicle for currency speculation, though, you'd generally want to be dealing with very large amounts of money. Currencies, after all, are at the very heart of the financial systems of nations, and those nations are much happier when their exchange rates are relatively stable, so it takes a lot of money on the fat end of the lever to make much money from the swings in the system.
And. of course, as with any fungible commodity, if there's a market, you can expect to find a futures market as well. But that's another story.
I won't say that individuals should avoid currency trading. But I would recommend talking to a local investment expert. Who would probably advise making it a part of a larger investment plan at best.
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