Web app
An application that runs in the browser with nothing to install, like Gmail or Figma. The default form of modern software.
What it tells you about a developer
Web app experience is the industry default, so the signal is in which half they own and how deep it goes. Some developers have shipped a complete public web app alone, visible as one repository holding frontend, backend, and deployment configuration. That is full-stack range with a live artifact you can open.
A web app is software delivered through a URL: nothing to install, updated instantly for everyone, and running on any device with a browser. Most of the software industry builds web apps. That is why frontend and backend, the two halves of a web app, are the two biggest developer disciplines. Native mobile apps install from an app store.