If someone has emailed you, in Gmail, a PowerPoint and you want to be collaborative, you can open the PowerPoint right in Google Drive. No office software required.
Find the Attachment
Hover over the attachment to notice different options. You can download the PowerPoint by clicking on the down arrow. You can alternatively save the PowerPoint as a PowerPoint into your Google Drive by clicking on the drive icon.
Click on the Attachment
Clicking on the attachment, not the icons, opens the PowerPoint in preview mode. You can scroll through the slides without launching the PowerPoint in Office or in Google Drive.
Notice down in the bottom right is a blue button to “Open With.” Choose to open with “Google Slides.” This will create a copy of the PowerPoint and convert it to Google Slides presentation. This is now able to be edited and shared.
Is the conversion perfect? No, but overall it is pretty darn good. I have found I need to edit a few slides to make sure the text boxes are the right size. Frequently I just leave it the way it converts it, the conversion is fairly decent.