Polling is a one of the technologies to communicate data in real-time operation. In the real-time communication of data, it has to be achieved sending data in the smallest delay as possible.
it takes a time to sensing an environment and sending the obtained data. For example, in the case of human beging, time delay between sensing and movement is about 0.2 second. Shorter delay-time brings a better responce to realize the real-time movement or other reactions.
In also a robot programing and intelligence, short responce-time brings better real-time performance. This means that a short sending time is needed to realize the real-time intelligence to move the robot.
It is simple to realize the polling in sending data. The speed of recieving data should be faster than that of sensing. For example if it would take 0.1 sec. to sense environment, the program is able to send data about 10 times in a second. This is called 10 Hz or 10 fps to send data. In this cace, if a program recieves the data 10 time in a second, that is 10 Hz in recieving data, every data are received in the same timing.
On the other hand, if the speed of receiving program is slower than 10 Hz, for example 5 Hz, every data can NOT be recieved in a second. 5 data are stucked in a buffer of sending system. And it takes double time to recieve every data. This situation brings huge delay time in the sending data.
This is a simple principle in order to realize the polling that is a real-time property.
An example is shown in following figure in which some polling are used simultaneously.
For example acceleration and gyro sensor send data in about 1000Hz. So the speed of receiving the data should be faster than 1000Hz on sensory motor mapping module.
On the other hand, ultrasonic sensor has only 14Hz as its speed of sensing. Basically this speed becomes a speed of sendign the data of ultrasonic sensor. It is obvious that this speed is considerably slower than that of receiving module. Because of the receiving module has a speed faster than 1000Hz in this case. This is a reason why we should use noblocking receive in order not to be blocked for other faster communication of data.
Continuations are described in polling wiki.
See also Wikipedia as a reference.