UTC, coordinated universal time, defines a worldwide time that is valid to any place on earth. If it is for a citizen in Germany 10:00 UTC, it is also for a citizen in America 10:00 UTC. The intent to define such an era was, as the name suggests, the desire to coordinate global activities to. UTC has special significance for the marine, aerospace, and especially for the Internet.
On the basis of this coordinated universal time, time zones are determined, in which specified time offsets are applied. This makes it possible to define regional times which allow the dayly routine for the people. The origin (time offset ±0) of the UTC falls on the zero meridian in Greenwich (London - United Kingdom).
In addition to the offsets in the individual time zones there are national offsets, such as daylight saving time. The summer time is applied in addition to the regular offset.
For Germany:
CET (Central European Time): UTC+1:00
CEST (Central European Summer Time): UTC+2:00