Why grooves/deep lines create on tyres?

Can anyone explain the reason that why there grooves/deep lines creates on tyre during manufacturing? A detailed technical answer require.

Tyre-1.jpg

To make cool tire designs on dirt :D

But seriously, to add more friction between the tyre and the ground for grip so the vehicle won't easily slip while speeding up/down/stopping or steering sideways. On a plane and smooth road, these tire grooves also act as sort of air lock at high speeds adding more to the vehicle's grip to the road/ground due to pressure of air hitting the car which act as the downward push, pressing the vehicle to the ground and hence, the tires...

That's why ~200km/k speed is enough for a plan to take off the ground but a car at 200km/h or over doesn't fly. Basically its shape dependent.

and that's exactly why people change tires after sometime, especially when the grooves on the tire are worn out or flattened.

Faisal already gave very nice explanation. I'll just add, just think of the reason that we have finger prints. They allow us to have better grip. Similarly, these grooves give tires better grip on road. And this "grip" comes from by increasing resistance or friction. Newton's second law of motion. :)

The groves increase the surface area and hence the friction/grip.