Okay kiddo, so let me explain pull technology to you in a way that you can understand.
Do you remember when you asked your mom to get your favorite toy out of your toy box? She went to the toy box and then brought your toy back to you, right? That's basically what pull technology is like.
When you use pull technology, you tell your computer or phone that you want it to go and get something for you, like a new message or photo. Then, the computer goes and "pulls" that information from wherever it is stored (like on a server or another device) and brings it back to you.
This is the opposite of push technology, which is more like your mom giving you a toy without you having to ask for it. With push technology, things like notifications or updates are sent directly to your device without you having to actively request them.
So, to sum it up, pull technology is like asking for something and then getting it, while push technology is more like things automatically being sent to you without you requesting them.