Upvote:5
It relates to the character, conduct, and associations of an individual wanting to enter the UK https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/827971/GGFR-Section-1-v29.0-EXT.PDF
For example:
• a person is a member of a proscribed group
• a person is suspected of war crimes or crimes against humanity
• a person’s presence is undesirable because of their character, conduct or associations
• a person’s presence might lead to an infringement of UK law or a breach of public order
• a person’s presence may lead to an offence being committed by someone else
Upvote:9
It is a general catch-all for keeping people out who might engage in criminal, anti-social or politically divisive activity.
It literally means: "Is the presence of this individual in the UK going to be good for the UK public?"