Forming a beam (directional gain) and, sometimes, shifting the beam direction.
Beam forming refers to shifting the beam direction in order to obtain maximum response from the provided direction and minimize the response coming from unwanted directions.
This can be done mechanical by turning the antenna face to the respective direction or by digital method. Digital method utilizes the shift of the wave (phase or time delay) at each antenna element when coming from different directions. The antenna elements are multiplied with the weight vector to obtain the beam shift in provided direction.
There are different types of beam forming algorithm such as phase shift beamformer (conventional beamformer), minimum variance distortionless response (MVDR) beamformer and linear constraint minimum variance beamformer (LCMV) etc.