A patch is a software update that fixes bugs. You are granted access to the patch by Talend Support and you can download and apply it either via Talend Administration Center or manually.
The processes for applying the patch are different for Talend Studio/Talend CommandLine patches and other types of patch (such as ESB patches).
All Talend Studio clients connected to the same project must install the same patch. Updating a Studio connected to a project requires all the Studios connected to that project to be updated.