can someone explain to me what security guard means?

[dat feel]

NYPD Looking For Band Of Thugs Who Walked Into A Lululemon And Casually Walked Out With Nearly 30k Dollars Worth Of Items

Police in New York City are looking for seven people who they say stole around $30,000 from a Lululemon store in Manhattan. The incident happened on Tuesday at around noon when four males and three females entered a Lululemon store located at 400 West 14th Street and stole approximately $28,780...

vidmax.com

i don't think i understand the duties of a security guard