How work Raw Ir decoder?

Using Arduino Programming Questions
1

Hello.I need help to understand how work Raw Ir decoder sketch?Why pin 2 is still high?Sensor tutorials - IR remote receiver/decoder tutorial
The Ir pulse is 01010101....with frequency 38KHz when pulse Ir is high....how counter work when fall to zero for 13usec?

2

Is this a different question to http://arduino.cc/forum/index.php/topic,88484.0.html