When you click a Gmail attachment, Google lets you preview its content inside Gmail. You can also save the file to Google Drive, but it's not converted automatically to a format that can be edited by Google's apps.
Google Docs, Slides and Sheets now support "15 new Office formats - including presentation show files (PPS, PPSX), macro-enabled files, and template files - all with improved charts, images, and tables support." Unfortunately, macros will be removed from macro file formats upon conversion. Here's the full list of new formats that can be converted:
* DOT, DOTX, DOTM, DOCM - Word files
* XLT, XLTX, XLTM, XLSM - Excel files
* POT, POTX, POTM, PPTM, PPS, PPSX, PPSM - PowerPoint files
If you'd like to edit files without converting them to Google's formats, you can use this Chrome extension.