| Serverless web apps. Using their own Next.js as an example: everything in /pages/ is client app, everything in /api/ is serverless app. Client talks to the /api/ endpoints, /api/ endpoints talk to your domain services. Vercel also provide edge-location hosting and caching. |
They have a suite of complementary software products and services, including NextJS (a "batteries included" React framework with robust support for SSR and SSG), Now (hosting / CDN / runtime in "serverless" paradigm), Micro, etc.
World-class DX and remarkably powerful tools that somehow combine simplicity and flexibility.
No affiliation, just a longtime grateful fan.