The company through which a huge part of the internet accepts card payments - invisible, but without it most online stores stop working.
Stripe sells businesses a tool that takes card data. A small online shop drops a few lines of code onto its site and can now accept Visa, Mastercard, Apple Pay. Without Stripe, that same shop would have to negotiate with banks itself, pass security checks, and build a system that handles money - work that takes months, not an afternoon.
Example: you place an order at a small online boutique. The card form looks like part of the boutique's own site, but your data never reaches its servers. It goes straight to Stripe, which verifies the card, sends the money, and then transfers the merchant the rest - minus a small fee for the service.
The reason Stripe exists is simple - accepting card payments has always been bureaucratically closed off, reserved for banks and big companies. The Collison brothers turned it into something any programmer can plug in with a few commands. That's why it's growing fast - it serves millions of businesses, from one-person online shops to platforms like OpenAI.
Here's the flip side. When a whole industry runs through one piece of infrastructure, that infrastructure becomes a point of dependency. If Stripe shuts down a business's account - and it does, at its own discretion, on suspicion of fraud or risk - that business can't receive money, even if its product is entirely legal. Few people know that the checkout on the site they're shopping on actually belongs to a different company.
Hm, but look now
As an agency owner since 2009, I've watched this from the other side - a client wants a shop, and the real question is always who's going to take their money safely. Stripe made that question boring, and boring, in payments, is the best thing that can happen.
So when I build a system for a client, the choice is clear - I put in Stripe and don't reinvent the wheel. But I also remember the other side - I'm building something of someone else's into the foundation of my own business. It's convenient, while it works.