Advanced Installer - Tool Installer lets you install a particular version of Advanced Installer on your hosted agents. The version can be downloaded from the internet or the tools cache and is added to the PATH.
Advanced Installer - Build allows you to create a custom task in Team Services to build an Advanced Installer project. The hosted agent must have a version of Advanced Installer installed on it for this task to run.
Tool Installers are also supported for Team Foundation Server starting with TFS 2018.
Make sure you to install both extensions on your hosted agents and enable in Team Services the "Task tool installers”preview feature for your account. Next, you will have to add and configure the build tasks.
Tool Installer needs to run first because the Build task requires a version of Advanced Installer installed on the hosted agent.