so what do u use mercury for? receive money and sending money?
Yes, but also a bunch of stuff.
Mercury is not a bank. It is a banking service provider to non-resident US companies or businesses and of course to US residents also. They partner with banks the same way Payoneer would partner with some banks e.g. First Century bank, Federal Savings bank and blah. But it's way top notch than that. You get your corporate account organized and they have some other addons useful for corporate finance e.g. Quickbooks etc.
It's great if you are looking to carry your business forward 100% corporate and official as a non-resident LLC plus that's pretty much attractive to investors as it keeps your inflow and outflow a lot more organized so that you can export some financials at the end of a fiscal period. The same way you would, with any brick-and-mortar bank. Of course it's a real bank you are given. And again that makes it different than Wise and the likes.
Also useful to open some merchant accounts as you now have Corporate bank statement in checking account and in your company name (not personal name) which means higher chances of approval. Of course, for this to be meaningful, I would expect that you are cashing out payments from clients, Stripe, Paddle, 2checkout, Payoneer, Wise, WooCommerce, Shopify etc into this corporate checking account. Remit all payment into it (just in case you want investors or some proof for your future use case). That's the point!
Another top player like Mercury is the Silicon Valley Bank as someone already mentioned here. I prefer Mercury because it doesn't require monthly fee commitments, unlike the ongoing costs it takes to maintain your account with Silicon ValleyBank. Not sure the actual rates again. I'm just not interested in monthly commitments (fees) than I already incurred with registered agent ($40 per year) hosting, domain and a few others.