UTC is the time standard being followed by the world. Understanding of UTC requires understanding of few elements.
1)Apparent Solar Time: During Summer, you look up the sky and the sun is exactly above your head - That moment of time is the Local Noon for the place or for the meridian line you are standing on. If you continue to stand in the same place the next day, the sun will again pass through your head.
The time difference between the first meridian passing event and the second meridian event is one apparent solar day.
The length of this apparent solar day differs each day. The reason for this difference of length between any apparent solar day is because the earth rotates the Sun in the elliptical path.
2)Mean Solar Time:Now if there is a Sun, that passes through the meridian exactly at the same time every day - that Sun is called the Mean Sun. The time interval between the meridian passing of the Mean Sun is a day, Mean solar day or a Civil Day as per UTC.
As per UTC, every day consists of 24 hours and every hour consists of 60 minutes. Every second consists of 60 seconds.
3)UTC: UTC is within in 1 second difference of the Mean Solar Time in 0 degree longitude. UTC does not follow Daylight Saving Time. UTC precisely follows SI unit of seconds which in turn is followed by the Atomic Clocks. UTC is exactly follows the International Atomic Time minus leap seconds added so far.
4)Abbreviations and the governing bodies: UTC stands for Coordinated Universal Time in English or temps universel coordonné in French. UTC is the time standard used for civil timekeeping all over the world.
UTC time-scale is maintained by the BIPM - Bureau international des poids et mesures / International Bureau of Weights and Measures along with International Earth Rotation and Reference Systems Service(IERS).