This is a very difficult question to answer, because, Security encompasses so many different jobs!
- The entry-level HS graduate no-experience-necessary position/retiree looking for extra pocket money: Could be going from business to business rattling doors to make sure they are locked. Or standing at the gate of a retirement community waving the residents through and logging all visitors in.
- Could be working in a bank lobby, greeting customers, while watching for bad guys, who rarely show up (thankfully). Or at a corporate headquarters, escorting employees to their cars when they leave late at night.
- lots of other stuff in between . . . club bouncers. crowd control (football games)., Armored car, etc
- Dignitary protection - lots of high profile targets and their families who could easily be the victims of kidnapping - , all the way up to presidential election contenders/ Secret Service type stuff.
- Military security- guarding missiles, installations, prisoners, etc.
All of it requires a level of alertness and good people skills. You would also need to stay calm under pressure, work well with other agencies, and write good reports.
Hope this helps!