The word "guys" is a casual term used to refer to a group of people, typically friends or acquaintances, regardless of gender. It can be used to address a mixed-gender group or to refer to individuals in a friendly, informal context.
The term "guys" originally comes from the name Guy Fawkes, a 17th-century Englishman involved in a plot to blow up the Houses of Parliament. The word "guy" started to be used in the 19th century to refer to a poorly dressed man or a man in general, which eventually evolved into the plural form "guys" that we use today to refer to a group of people.