The Setup Wizard can be used to easily install and uninstall components, modules, and extensions, manage modules, upgrade your installation, and make changes to the Web setup of your installation.
The Web Setup Wizard is being deprecated in Magento 2.3.6 and will be removed in Magento 2.4.0. After it is removed, you must use the command line to install or upgrade Magento, as well as modules and extensions.
Important: Always flush the cache after installing or upgrading Magento, or any extensions and modules.
Extension Manager lists each component that is currently installed, and can be used to synchronize any extensions you have purchased from Magento Marketplace with your system.
Module Manager lists the components and modules that are currently installed in your Magento system.
The System Upgrade tool can be used to upgrade your installation of Magento. During the process, it checks your system for readiness, creates a backup, and then upgrades your system.