There are certain components like Apex Classes, AuraDefinitionBundles that are made from multiple files. Now when these components are edited in either a Deployment or a Branch, all the files are available for editing. e.g. previously if editing a class, only the .cls file could be edited but now the meta-xml file can also be edited along with the .cls file.
This is done using a tabbed interface when editing the component. Please refer to the screenshot below.