The section of the UE4 documentation on texture properties says this:
“texture compression settings: The compression settings to use when building the texture.”
I found this unhelpful. I, and I’m sure many others concerned with texture optimization, would greatly appreciate some reference on exactly what each of these compression options actually mean and which specific standards they use. Thank you.
Hey there! thanks for the heads up on this! I will put in a request to get better clarification on this subject 
thank you!
Along with this, it there anything other than just better clarification we could do to make this topic easier to understand. Just curious on my end, sometimes I know people like to see a comparison of the feature like a before and after sort of thing. Or sometimes a better explanation is just want is needed. Let me know if there is anything that could also help
Most of them are diffrent settings for mobile, where GPU supports different texture formats, if texture is not compressed in supported format you will have black texture rendered insted. Google them and you should have info about them and where they are used
There was a page on the UDK docs that went over normal map compression and it was really helpful but limited only to normal maps. Something that explains the way each format handles individual channels and why they are best suited for their in-editor namesakes (TC_NormalMap, TC_Masks, etc.) would clear up a LOT of second-guessing on my end. Many thanks for looking into it!
still no documentation 2 years after…