Aviator is a crash game. A plane on your screen flies higher and higher on a multiplier graph before suddenly flying away. You have to cash out your bet before the plane flies away.
Suppose you bet INR 100 in a round of Aviator. The plane takes off and the graph starts climbing up - x2, x3, x4... and so on. If the plane flies away before you are able to cash out, you lose your 100 bucks.
But if, let's say, you cash out at x3 (times 3) while the graph is still climbing, you win 3 times your initial bet!
All crash games are similar but they can be different themed.