"Hon" is short for "honey". It's a name that you can use for someone who's close to you. Here are some examples of when someone might use "hon":
- a mother speaking to one of her children
- a wife speaking to her husband
- an older woman talking to a younger coworker who's also a close friend
It's not as common for men to use "hon". You also wouldn't use it with your lover in a really romantic situation.