GRBs were discovered in 1967 by instruments of Vela mission satelite. This spacecraft was launched by the U.S. Department of Defense to search for nuclear explosions violating the Nuclear Test Ban Treaty. Soon after launching, the instrument detected the first event of gamma-ray burst, but this result was published 6 years later in 1973. Detailed study of these bursts revealed that they did not come neither from the Earth nor from the close Solar System and that they were a totally new class of cosmic objects. Today we know a lot about GRBs but they still keep many mysteries.