The most common cause of a tyre blowout is the pressure being too low. Here's why:
When a tyre is properly inflated, the sidewall is fairly stiff. There's enough 'give' in the sidewall, thanks to the pressure, to absorb normal bumps. However, the sidewall really doesn't flex that much in normal driving.
If a tyre develops a slow leak, however, the sidewall flexes more and more. At least the bit directly under the axle, subject to the car's weight, does. And then, as the car rolls forward, a new bit of the sidewall bends under the weight, while the bit that was bent like this just moments ago straightens back out.
This considerable flexing and un-flexing generates heat. So if you drive far enough on a seriously deflated tyre, it will generate enough heat to destroy the sidewall. When that happens, the remaining air is dumped out in a hurry -- which is inconvenient if you are halfway around a bend when this happens.
Tyres that blow out are not repairable -- and they have the capacity to cause crashes as well.
The best way to prevent blowouts is to monitor the pressures in your tyres regularly. Use a pressure gauge because it is almost impossible to evaluate the pressure in a modern radial tyre by eye. A modern radial tyre that loses half of its recommended air and is operating at only half the recommended pressure looks like ... a properly inflated radial tyre.
Inflate your tyres to (at least) the pressure recommended by the manufacturer, which is noted on the car's tyre placard.