NTP stands short for Network Time Protocol. This protocol (as it has been said in the name) is a protocol which allows computers to synchronize their time in a network of computers.
Now this NTP protocol is highly important because setting the exact time on a computer is highly important. One of the key points of the network time protocol is in its way of setting the time right. The time is set through satelites.
Satelites have control over to how precisely (precisely down to a nano-second) determine time and basically when a computer is working on a network it receives the information from the satelites, through the NTP protocol. Now, the NTP protocol coordinates itself through the UTC (Coordinated Universal Time).
The NTP protocol is not used in all the software around the world simply because it is not cost-effective. This protocol together with the UTC is used for example, to coordinate computers which coordinate flights so big catastrophes can be avoided.
If you are an owner of an internet-caffe, using the NTP protocol to set up the computers precisely at what the given time is, is to some even absurd. Missing a mili-second won’t bother you in finishing up all the procedures from computer to another or transferring data.