I was watching some battles on youtube and after the pokemon attacked on some it kept saying the pokemon hung onto its life. what does this mean?
So it appears my previous answer got hidden.
Again, i would believe it was a life orb, and this time i found a video of a Jolteon getting 10% life orb damage and it says "The foe's JOLTEON hung onto life!"
And i wasn't saying it always says it, but this is probably a rom, maybe translated from a japanese patch so that's why it doesn't say the same on your ds.
At 1:50 in this video.
That was probably the work of a Focus Sash, Sturdy, Endure, one of the moves that prevent Pokemon from getting Ko'ed although l'm not exactly sure which.
When it says this, it means that the Pokemon had a Focus Sash, or used any one of the moves that prevent a KO. Basically like MidnightSky said.
Hope this helps =)