SNTP is an acronym that stands for Simple Network Time Protocol. As its name suggests, it is a less complicated version of Network Time Protocol, which is a system for synchronizing the clocks of networked computer systems, primarily when data transfer is handled via the Internet. NTP, one of the oldest Internet protocols still in use, uses as its base a GPS clock or other type of radio clock, which can be scientifically accurate to a number of places past the traditional second in a timescale.
We don't necessarily need to keep such precise time in our everyday lives. Computers, however, need to implement very precise timekeeping. Especially computers that are networked together and, therefore, amenable to real-time data sharing need precise timekeeping in order to avoid run-time errors and data corruption. Two computers with time clocks that are just a fraction of a second off can be in for catastrophic data transfer failures.
Another reason to synchronize timekeeping for computers is to avoid such inverse causal relationships as the reply to the email that arrives before the original email was sent. This wouldn't literally be true, but it would appear to be so if the receiving computer was not telling the right time.
NTP is used for heavy-duty data transfers and networks that have a large number of workstations. SNTP is used for computers and computer systems that don't require such precise calculations in order to operate. For example, one computer hooked up to the Internet doesn't need the extreme power of NTP and can get by using SNTP, even when doing large-bandwidth data transfers. It's the multiple-workstation approach that requires the most detailed timekeeping.
Certain manufacturers offer devices such as SNTP servers, the primary purpose of which is to provide your computer or your network with precise time, based on Internet standards. NTP servers are available as well, for more extensive demands. No matter which version your computer is running, you are no doubt thankful that NTP and SNTP are around. Without them, certain basic operations could crash an entire network and certainly a personal computer.