while loops will loop continuously, and infinitely, until the expression inside the parenthesis, () becomes false. Something must change the tested variable, or the while loop will never exit. This could be in your code, such as an incremented variable, or an external condition, such as testing a sensor.
while(expression){ // statement(s) }
expression - a (boolean) C statement that evaluates to true or false
var = 0; while(var < 200){ // do something repetitive 200 times var++; }
Source: arduino.cc