Because they are yokels, the disciples admire the fancy buildings in Jerusalem. Jesus, however, is in a crappy mood and says ominously that all of it will be destroyed soon. The disciples want to know when all this will happen, and how they'll know it's the second coming and not, say, a random series of natural disasters. Jesus says first of all, don't believe anyone claiming to be him. Then don't worry about wars, because that's just the first stage, to be followed by famine, rebellion and earthquakes.
The disciples themselves can expect beatings, family strife and patricide. Lots of people will hate on them, but if they can survive it all, they'll be rewarded in the joyless, sexless heaven promised in chapter 12.
When they see the the abomination of desolation (v. 14) that Daniel talked about, they should flee to the hills without pausing to take their treasured possessions, clothing or pregnant wives. Oh, and it will be ever so much worse if all this happens in winter.
What will this abomination of desolation look like? Well, it will be hell on earth. No one would survive if god didn't shorten the days to spare the faithful. There will be plenty of false Christs with tricks to convince us they're the real deal. The sun and moon and stars will all be blacked out.
But in the end, Jesus will come back and save the chosen. All this will happen soon, within the disciples' own lifetimes. He can't be specific about times, though, because he isn't sure. Only god knows.