apt upgrade and apt dist-upgrade are both commands used to upgrade packages in Debian and Ubuntu systems. Their main purpose is to update installed packages to access the latest features and fix vulnerabilities.

Although they are both used for updating packages, there are some differences between them:

1. apt upgrade: The apt upgrade command is designed to upgrade the currently installed packages to their latest versions. It compares the versions of the installed packages with the versions available for download and upgrades only those packages that have new versions. The apt upgrade command only updates the versions of installed packages and does not install new packages or remove any existing ones. Therefore, it is suitable for routine system package updates.

2. apt dist-upgrade: The apt dist-upgrade command not only upgrades the installed packages but also intelligently handles dependencies and performs broader changes, which may include installing new packages or removing old ones. Unlike apt upgrade, apt dist-upgrade will install new packages, remove obsolete ones, or adjust the dependencies of existing packages as needed to ensure that all system packages can be appropriately upgraded.

In practice, it is generally advisable to prioritize the use of the apt upgrade command for regular package updates. The apt dist-upgrade command should be considered only when certain packages cannot be upgraded due to dependency issues.

Please note that before performing any package update operations, it is recommended to back up your system data to prevent any unexpected situations during the process.

Summary: apt upgrade and apt dist-upgrade are commands used to update software packages. apt upgrade is used to upgrade the versions of installed packages, while apt dist-upgrade not only upgrades packages but also manages dependencies and performs broader changes. When in use, it is better to prioritize apt upgrade for routine updates, resorting to apt dist-upgrade only when encountering dependency issues.