why important packages in require-dev ? and not in require ?

        "dotkernel/dot-navigation": "^3.1",
        "dotkernel/dot-flashmessenger": "^3.1.1",
        "laminas/laminas-form": "^3.1.1",
        "doctrine/doctrine-module": "^5.1",
        "mezzio/mezzio-authorization": "^1.4"

why those packages are in require-dev ?