What is HPBW (half-power beamwidth)?

Half Power Beam Width is an angular width. It is estimated on the major lobe of an antenna radiation pattern at half-power points
at which the signal power is half that of its peak value. At the point when a line is drawn among the radiation pattern’s starting point and the half power points on the major lobe, on both the sides, the angle between those two vectors is named as HPBW, half power beam width.