explain while loop

Answer 1

While loop structure is:

while ( <condition> ) {
/* code to execute many times ( looping ) */
}

This means: repeat the block of code inside the brackets, WHILE the <condition> is true...
<condition> is any instruction which return a result who could be interpreted as true or false.

[ EDIT ]
<condition> is tested before the block runs, so the block can be never executed if the condition is false the first time the <condition> is evaluate...