From the publisher's website...

The basic concept is very simple. You pick a card that has a word on it. Your team has to guess the word within 90 seconds by asking you any question and as many questions as they like. But the catch is, you can only answer in 'Yes' and 'No'. A few more answers like ‘May be’ or ‘I don’t know’ are allowed for obvious reasons. If your team cracks the word, it wins and rolls a dice to move its pawn on the scoreboard. There are bonus points for difficult words! Words have been very carefully selected to have fun & challenge together.