Fundamental questions of the theory of gravitational waves are considered, and the properties of these waves are compared with those of electromagnetic waves. The efficiency of possible sources of gravitational radiation, both astronomical and in the laboratory, is analyzed. The principles on which detecting devices work are explained and their sensitivities are estimated. Particular attention is devoted to a new direction--the emission and detection of gravitational waves by means of electromagnetic systems. One of the variants of a laboratory experiment including a source and detector of electromagnetic type is described. The mechanism by which an isotropic blackbody background radiation of gravitons could have been formed is discussed, together with possibilities for detecting it.