It's all here in this NASA paper:
ntrs.nasa.gov
To summarize it's a paper about field propulsion, some kind of warp-drive using lasers and magnets, nothing tinfoil here, we all know that it's allowed by Einstein's equations and that NASA Eagleworks has been openly working on these things for years.
Here's where it gets weird: Right off the bat they start mentioning UFOs claiming to "not be involved in UFO research". Why mention UFOs? it's just a physics paper.
Then it gets weirder: Despite this disclaimer, the entire paper is essentially them admitting that UFOs could be real aliens and we should study the phenomena with "photographic spectra", "magnetic measurements" and "geiger counters" in order to glean information about their propulsion systems. In short, stories of scientists prodding crashed spacecraft in Area 51 is bunk, it's really about monitoring emissions from UFOs in the sky.
Finally there's the picture that I have included in the bottom half of pic related. NASA's ideas for a field propulsion craft; it looks exactly like the famous UFO that was seen in 1947.
So the take-home message from this is not that aliens are real, this isn't proof of that but that NASA does take the idea of space aliens seriously. Not only that but they are actively involved in studying UFOs and have even gained something from it.