x means don't play that string at all. o means play that string open.
The dashes are just spacers, presumably some kind of timing device (there are 36 'zones' in a 'bar'). And although this would be a good idea, I don't think it's employed here, as the guitar starts at the very beginning of the bar - the chords shown don't!
The dashes actually do not mean don't play. If we go by the track, the chord played before the dashes actually rings on, until the next chord. This is one (of many for me!) problem with this sort of tab - it doesn't give as much detail as 'proper' music, in that unless there are notes or their stems shown as well, unless one knows how the song goes, one cannot know how the timing goes. And if one knows the song, then one is at least half-way to playing it anyway. Rave over!
So, basically, it means very little! Presumably, you've listened to the song. That will most likely give far more clues than blindly following what someone has tabbed. Seriously!
That apart, if you're learning piano, it's somewahtsomewhat counter-productive to try to translate guitar tab (especially as you don't play guitar!). You will be better off finding proper piano music, and learning to translate that. Honest!