A Laravel application does not run on its own. It needs a particular PHP version, a database, usually Redis and sometimes a search service. If everyone involved sets that up by hand on their own machine, small differences appear, and small differences turn into faults that show up for one person only.
Docker describes that environment as a file inside the project. Somebody joining fetches the project and starts it instead of spending a day on installations. Laravel ships a ready-made arrangement for this called Sail.
What it means for a project
The benefit shows in two places. When new people join, because a day becomes an hour. And at version changes, because a jump from one PHP version to the next can be tried out safely by changing one line.
It is not free. Docker is one more thing that wants understanding, and on some machines it costs noticeable speed. On a small project with one steady developer the benefit is limited. As soon as several people are involved, or the project is meant to run for years, the balance tips.