I'm working on a project and a new user of Github I'm not sure I understand the difference between merging and deployment.
Working with pull requests, sometimes I see:

The PR is still open.
Where as sometimes I see some pull requests not deployed and not merged:

Obviously I see the difference, when it's deployed I can see the change on the website. And when I'm sure the result is good I can merge the request. The question is, how can I deploy a PR without the merging, is there a command?
Thanks.