.DRA: DaVinci Resolve Archive – This is a folder with all the projects and media inside. These are great for putting EVERYTHING from your project in one place, or for transferring to another drive, sending online, etc.
.DRP: DaVinci Resolve Project – This is just a project file exported from Resolve. These are very small, and just outline how media is edited and put together. There are NO MEDIA FILES included.
.DRT: DaVinci Resolve Timeline – This is a SINGLE TIMELINE from a Resolve project. Great if you want to transfer JUST ONE timeline from a project and bring it into another. This is a very small file with NO MEDIA.