Templates are for starting from something more complete than a blank service: a curated stack — often an app plus the backing service it needs — deployed together, in one click, from a prebuilt image rather than a build.
Deploying a template
"Deploy" on any card opens a picker: drop the template into any existing project, or type a name to spin up a new one on the spot — no need to leave the gallery to create a project first.
Because it's a prebuilt image, deployment skips the build step entirely, the same way Deploying a Docker image does — the difference is a template can provision more than one service at once, wiring them together automatically.
Note. Everything from here on — logs, environment variables, custom domains, settings — works exactly the same as a service deployed from Git or Docker. Templates only change how a service starts existing, not how it's operated afterward.