Viewed from above, the task in each level of X-It is to create a path to walk through to the exit, by moving blocks around a walled arena. The movement physics are fairly true to real life - most blocks can only be pushed if there is a block's worth of space behind them, and nothing immediately ahead of them.
The levels are full of gaps, through which blocks can be pushed - this has the double effect of freeing up extra room in the level, and allowing you to walk over those spaces. Other hazards include ice which prevents blocks from stopping until they go past it. Falling through holes loses you one of your 3 lives - you also have 5 attempts at each screen.