Whats difference in the 400 meter indoors then outdoors?

Indoors it's 2 laps because each lap is 200m. However on an outdoor track it's one lap because each lap is 400m. If you compare the times of the indoor and the outdoor times, you will see that the outdoor times are usually better. Sometimes, it's good to compete in the indoor 400 metres because the weather, doesn't affect significantly what your time will be. In the outdoor, hot weather, rainy weather etc, can affect your time.