Beam forming is a special microphone positioning technique that allows FILTER to focus its microphone array onto sound coming from a particular area in front of the speaker, while 'filtering' out and reducing/omitting sounds coming from outside of this cone shaped area.
Depending on your beam forming setting, the cone of focus can be made wide, medium, or narrow. It can also be turned off completely. Note that beam forming introduces a bit of noise suppression that is not linked to the Noise Suppression options. The more focused (narrow) the beam forming cone is, the higher the suppression will be for sounds outside of its cone of focus.
This function is great for when you want clear audio from a specific direction but would rather keep the audio pickup away from others (like if you're in a cafe and would prefer to have only your voice picked up, rather than the people sitting in front of you).
Beam forming should be set according to how many speakers are present, and how the FILTER will be used. For example, if it's a single user sitting at a desk, a narrow beam forming mode is going to give you the most isolation and call quality. On the other hand, if you're using FILTER while moving around, in a larger space, or speaking with multiple people in a conference setting, a beam forming setting of wide or off (which would mean a 360 pickup) is probably more appropriate.
Note that beam forming used in conjunction with the AI Noise Suppression options and can impact sound quality of your voice. An inappropriate beam forming setting may lessen the effective scope of the AI noise cancellation, so be mindful of your positioning when you have beam forming enabled!