A number of Android phones can capture RAW photos now, but editing them on Android is tricky. There are a few apps that do it, but they're clunky or as in the case of Lightroom, cost money. Now Google's free Snapseed editor has been updated to v2.1 with RAW editing tools. We've got the APK on APK Mirror if you want to take it for a spin.
A RAW file is simply the full output of the sensor, which offers more powerful editing options than you get with a compressed JPEG. Devices like the LG G4 and Galaxy Note 5 can capture RAW files with the native cameras, and still more phones like the Nexus 6P, 5X, and 6 have the Camera2 API that allows third-party apps to do the same. However you do it, you'll have a DNG file that can't be opened by standard photo editors.
The new version of Snapseed does have RAW support, but it's not the most intuitive experience. When you open a photo, you'll need to switch from the standard Android file picker to a file manager in order to see the RAW files (don't accidentally open the JPEG). When you pull up a RAW file in Snapseed, it immediately loads the develop tool with options for exposure, highlights, temperature, and more. From there, you can access any tool you want and save the result as a JEPG. It's pretty rad.
- +Anton Daubert