Why is there lightning before the thunder?

I love thunderstorms, and understand how thunder works (hot and cold air), but why is there lightning first before the clap of thunder? And how is the lightning "made"?

Lighting is seen so it moves at the speed of light which is faster than the speed of sound that thunder moves at. Lighting is electricity discharging from the cloud to the ground.

Thunderstorms often occur at the end of hot, sticky summer days. At this time, warm moist air rises quickly and forms large cumulonimbus clouds. Inside these tall dark clouds, air currents create strong updraughts and water droplets and ice particles rub against each other. As they bang together like this, it causes a build-up of static electricity. Lighter, positive charges gather at the top of the cloud and heavier, negatively-charged pieces of ice and water accumulate at the base. The ground below is also positively charged. Electricity flows between the charges and the difference between them increases. When the differences get big enough, they are neutralised and electricity is released as a flash of lightning.