Another vote for the Zeiss although I haven't looked through the Swarovski. If they are the same price it'd be tough but I'm pretty sure the Zeiss costs less and I know it's a great scope for the price. Have Zeiss Conquest binos too and they are just as nice.

Parallax is basically the focus of the scope. Scopes without the adjustment have the focus set at around 150 yards. Your eye can adjust the focus up close and farther away on those. Once you start getting to the higher magnifications your eye can't ajust enough any more so you'll have to adjust the parallex to get the correct focus on longer or closer targets.