The goal of exploring a room is to find all the objects hidden in it in a limited time. The list of items to find is to the right of the room, with a timer at the top.

Each item you find brings points. The amount depends on how much the combo-bar at the top of the screen is filled. The faster you find items and the fewer mistakes you make, the longer you can keep that bar at maximum.
Be careful: any wrong tap will reset the combo bar! Several consecutive faults will shorten the exploration time.
Find all the items before time expires, and you will receive experience, coins and items as a reward. If you don't have enough time, you can always buy extra for Diamonds or add some for watching video ads.

After exploring the room, the total number of points you earned is calculated and your Mastery Level for this room increases. The more points you have, the higher your room exploration rating is among guild members.